[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-clang-x86_64-expensive-checks-debian` running on `gribozavr4` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/16/builds/6156

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

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
...
3.465 [2/31/695] Linking CXX executable unittests/Target/VE/VETests
3.511 [2/30/696] Linking CXX executable unittests/Target/WebAssembly/WebAssemblyTests
3.549 [2/29/697] Linking CXX executable unittests/Target/PowerPC/PowerPCTests
3.626 [2/28/698] Linking CXX executable unittests/tools/llvm-cfi-verify/CFIVerifyTests
3.724 [2/27/699] Linking CXX executable unittests/Transforms/Coroutines/CoroTests
3.753 [2/26/700] Linking CXX executable unittests/Transforms/Instrumentation/InstrumentationTests
3.807 [2/25/701] Linking CXX executable unittests/Target/ARM/ARMTests
3.859 [2/24/702] Linking CXX executable unittests/Target/RISCV/RISCVTests
3.914 [2/23/703] Linking CXX executable unittests/Transforms/Utils/UtilsTests
3.956 [2/22/704] 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++ -DEXPENSIVE_CHECKS -DGTEST_HAS_RTTI=0 -DLLVM_BUILD_STATIC -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GLIBCXX_DEBUG -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/b/1/llvm-clang-x86_64-expensive-checks-debian/build/unittests/SandboxIR -I/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/unittests/SandboxIR -I/b/1/llvm-clang-x86_64-expensive-checks-debian/build/include -I/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/include -I/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/third-party/unittest/googletest/include -I/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/third-party/unittest/googlemock/include -U_GLIBCXX_DEBUG -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-clang-x86_64-expensive-checks-debian/llvm-project/llvm/unittests/SandboxIR/RegionTest.cpp
/b/1/llvm-clang-x86_64-expensive-checks-debian/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.
4.072 [2/21/705] Linking CXX executable unittests/Target/AArch64/AArch64Tests
4.143 [2/20/706] Linking CXX executable unittests/ExecutionEngine/Orc/OrcJITTests
4.178 [2/19/707] Linking CXX executable unittests/Passes/PassBuilderBindings/PassesBindingsTests
4.213 [2/18/708] Linking CXX executable unittests/Analysis/AnalysisTests
4.302 [2/17/709] Linking CXX executable unittests/Transforms/Scalar/ScalarTests
4.651 [2/16/710] Linking CXX executable unittests/MC/AMDGPU/AMDGPUMCTests
4.656 [2/15/711] Linking CXX executable unittests/IR/IRTests
4.698 [2/14/712] Linking CXX executable unittests/Target/X86/X86Tests
4.759 [2/13/713] Linking CXX executable unittests/Passes/Plugins/PluginsTests
4.901 [2/12/714] Linking CXX executable unittests/ExecutionEngine/MCJIT/MCJITTests
5.068 [2/11/715] Linking CXX executable unittests/tools/llvm-exegesis/LLVMExegesisTests
5.096 [2/10/716] Linking CXX executable unittests/tools/llvm-mca/LLVMMCATests
5.641 [2/9/717] Linking CXX executable unittests/Target/AMDGPU/AMDGPUTests
6.226 [2/8/718] Linking CXX executable unittests/MIR/MIRTests
6.732 [2/7/719] Linking CXX executable unittests/CodeGen/CodeGenTests
6.775 [2/6/720] Linking CXX executable unittests/DebugInfo/DWARF/DebugInfoDWARFTests
6.790 [2/5/721] Linking CXX executable unittests/Target/TargetMachineCTests
6.909 [2/4/722] Linking CXX executable unittests/MI/MITests
7.180 [2/3/723] Linking CXX executable unittests/CodeGen/GlobalISel/GlobalISelTests
7.399 [2/2/724] Linking CXX executable tools/lld/unittests/AsLibAll/LLDAsLibAllTests
7.443 [2/1/725] Linking CXX executable tools/lld/unittests/AsLibELF/LLDAsLibELFTests
ninja: build stopped: subcommand failed.

```

</details>

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