[llvm] [SandboxIR][NFC] Move Instruction classes into a separate file (PR #110294)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lldb-aarch64-windows` running on `linaro-armv8-windows-msvc-05` while building `llvm` at step 4 "build".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/141/builds/2767

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 4 (build) failure: build (failure)
...
      |                ::llvm::
In file included from C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\lib\SandboxIR\Constant.cpp:9:
In file included from C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Constant.h:21:
In file included from C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Context.h:14:
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Type.h(61,16): warning: unqualified friend declaration referring to type outside of the nearest enclosing namespace is a Microsoft extension; add a nested name specifier [-Wmicrosoft-unqualified-friend]
   61 |   friend class TargetExtType;      // For LLVMTy.
      |                ^
      |                ::llvm::
5 warnings generated.
102.002 [5102/10/1317] Building CXX object lib\SandboxIR\CMakeFiles\LLVMSandboxIR.dir\BasicBlock.cpp.obj
FAILED: lib/SandboxIR/CMakeFiles/LLVMSandboxIR.dir/BasicBlock.cpp.obj 
ccache C:\Users\tcwg\scoop\apps\llvm\current\bin\clang-cl.exe  /nologo -TP -DGTEST_HAS_RTTI=0 -DUNICODE -D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS -D_HAS_EXCEPTIONS=0 -D_SCL_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS -D_UNICODE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -IC:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\lib\SandboxIR -IC:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\lib\SandboxIR -IC:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\include -IC:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include /DWIN32 /D_WINDOWS   /Zc:inline /Zc:__cplusplus /Oi /Brepro /bigobj /permissive- -Werror=unguarded-availability-new /W4  -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported /Gw /O2 /Ob2 /DNDEBUG -std:c++17 -MD  /EHs-c- /GR- /showIncludes /Folib\SandboxIR\CMakeFiles\LLVMSandboxIR.dir\BasicBlock.cpp.obj /Fdlib\SandboxIR\CMakeFiles\LLVMSandboxIR.dir\LLVMSandboxIR.pdb -c -- C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\lib\SandboxIR\BasicBlock.cpp
In file included from C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\lib\SandboxIR\BasicBlock.cpp:9:
In file included from C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/BasicBlock.h:13:
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Value.h(143,16): warning: unqualified friend declaration referring to type outside of the nearest enclosing namespace is a Microsoft extension; add a nested name specifier [-Wmicrosoft-unqualified-friend]
  143 |   friend class GlobalValue;           // For `Val`.
      |                ^
      |                ::llvm::
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Value.h(145,16): warning: unqualified friend declaration referring to type outside of the nearest enclosing namespace is a Microsoft extension; add a nested name specifier [-Wmicrosoft-unqualified-friend]
  145 |   friend class GlobalObject;          // For `Val`.
      |                ^
      |                ::llvm::
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Value.h(153,16): warning: unqualified friend declaration referring to type outside of the nearest enclosing namespace is a Microsoft extension; add a nested name specifier [-Wmicrosoft-unqualified-friend]
  153 |   friend class Module;                // For `Val`.
      |                ^
      |                ::llvm::
In file included from C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\lib\SandboxIR\BasicBlock.cpp:10:
In file included from C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Context.h:14:
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Type.h(61,16): warning: unqualified friend declaration referring to type outside of the nearest enclosing namespace is a Microsoft extension; add a nested name specifier [-Wmicrosoft-unqualified-friend]
   61 |   friend class TargetExtType;      // For LLVMTy.
      |                ^
      |                ::llvm::
In file included from C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\lib\SandboxIR\BasicBlock.cpp:11:
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Instruction.h(369,16): warning: unqualified friend declaration referring to type outside of the nearest enclosing namespace is a Microsoft extension; add a nested name specifier [-Wmicrosoft-unqualified-friend]
  369 |   friend class UnaryInstruction;
      |                ^
      |                ::llvm::
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Instruction.h(1100,9): error: base class 'SingleLLVMInstructionImpl<llvm::UnaryInstruction>' has private constructor
 1100 |       : SingleLLVMInstructionImpl(ID, Opc, LLVMI, Ctx) {}
      |         ^
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Instruction.h(362,3): note: implicitly declared private here
  362 |   SingleLLVMInstructionImpl(ClassID ID, Opcode Opc, llvm::Instruction *I,
      |   ^
5 warnings and 1 error generated.
102.110 [5102/9/1318] Building CXX object lib\SandboxIR\CMakeFiles\LLVMSandboxIR.dir\Module.cpp.obj
In file included from C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\lib\SandboxIR\Module.cpp:10:
In file included from C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/SandboxIR.h:112:
In file included from C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Argument.h:13:
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\llvm\include\llvm/SandboxIR/Value.h(135,16): warning: unqualified friend declaration referring to type outside of the nearest enclosing namespace is a Microsoft extension; add a nested name specifier [-Wmicrosoft-unqualified-friend]

```

</details>

https://github.com/llvm/llvm-project/pull/110294