[llvm] [SandboxIR][NFC] Move Region from SandboxVectorizer to SandboxIR. (PR #110173)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-x86_64-debian-dylib` running on `gribozavr4` while building `llvm` at step 7 "test-build-unified-tree-check-llvm".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/60/builds/8756

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

```
Step 7 (test-build-unified-tree-check-llvm) failure: test (failure)
...
0.869 [3/11/686] Building CXX object unittests/Target/AMDGPU/CMakeFiles/AMDGPUTests.dir/AMDGPUUnitTests.cpp.o
0.872 [3/10/687] Building CXX object unittests/Target/AMDGPU/CMakeFiles/AMDGPUTests.dir/DwarfRegMappings.cpp.o
1.341 [2/10/688] Linking CXX executable unittests/Target/WebAssembly/WebAssemblyTests
1.352 [2/9/689] Linking CXX executable unittests/Target/LoongArch/LoongArchTests
1.544 [2/8/690] Linking CXX executable unittests/Target/ARM/ARMTests
1.546 [2/7/691] Linking CXX executable unittests/Target/VE/VETests
1.606 [2/6/692] Linking CXX executable unittests/Target/RISCV/RISCVTests
1.624 [2/5/693] Linking CXX executable unittests/Target/AArch64/AArch64Tests
1.727 [2/4/694] Linking CXX executable unittests/tools/llvm-mca/LLVMMCATests
1.854 [2/3/695] Building CXX object unittests/SandboxIR/CMakeFiles/SandboxIRTests.dir/RegionTest.cpp.o
FAILED: unittests/SandboxIR/CMakeFiles/SandboxIRTests.dir/RegionTest.cpp.o 
CCACHE_CPP2=yes CCACHE_HASHDIR=yes /usr/bin/ccache /usr/bin/clang++ -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/b/1/llvm-x86_64-debian-dylib/build/unittests/SandboxIR -I/b/1/llvm-x86_64-debian-dylib/llvm-project/llvm/unittests/SandboxIR -I/b/1/llvm-x86_64-debian-dylib/build/include -I/b/1/llvm-x86_64-debian-dylib/llvm-project/llvm/include -I/b/1/llvm-x86_64-debian-dylib/llvm-project/third-party/unittest/googletest/include -I/b/1/llvm-x86_64-debian-dylib/llvm-project/third-party/unittest/googlemock/include -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -Wno-variadic-macros -Wno-gnu-zero-variadic-macro-arguments -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -Wno-suggest-override -std=c++17 -MD -MT unittests/SandboxIR/CMakeFiles/SandboxIRTests.dir/RegionTest.cpp.o -MF unittests/SandboxIR/CMakeFiles/SandboxIRTests.dir/RegionTest.cpp.o.d -o unittests/SandboxIR/CMakeFiles/SandboxIRTests.dir/RegionTest.cpp.o -c /b/1/llvm-x86_64-debian-dylib/llvm-project/llvm/unittests/SandboxIR/RegionTest.cpp
/b/1/llvm-x86_64-debian-dylib/llvm-project/llvm/unittests/SandboxIR/RegionTest.cpp:9:10: fatal error: 'llvm/Transforms/Vectorize/SandboxVectorizer/Region.h' file not found
#include "llvm/Transforms/Vectorize/SandboxVectorizer/Region.h"
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
2.224 [2/2/696] Linking CXX executable unittests/tools/llvm-exegesis/LLVMExegesisTests
2.609 [2/1/697] Linking CXX executable unittests/Target/AMDGPU/AMDGPUTests
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/110173