[clang] [HLSL] Introduce address space `hlsl_constant(2)` for constant buffer declarations (PR #123411)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `flang-aarch64-dylib` running on `linaro-flang-aarch64-dylib` while building `clang` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/50/builds/9388

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

```
Step 5 (build-unified-tree) failure: build (failure)
...
690.015 [1977/1/4844] Building CXX object tools/mlir/lib/Dialect/Linalg/Transforms/CMakeFiles/obj.MLIRLinalgTransforms.dir/BubbleUpExtractSlice.cpp.o
690.101 [1976/1/4845] Building CXX object tools/mlir/lib/Conversion/FuncToSPIRV/CMakeFiles/obj.MLIRFuncToSPIRV.dir/FuncToSPIRVPass.cpp.o
690.149 [1975/1/4846] Building CXX object tools/mlir/lib/Dialect/Transform/Transforms/CMakeFiles/obj.MLIRTransformDialectTransforms.dir/CheckUses.cpp.o
690.204 [1974/1/4847] Building CXX object tools/mlir/lib/CAPI/IR/CMakeFiles/obj.MLIRCAPIIR.dir/AffineMap.cpp.o
690.299 [1973/1/4848] Building CXX object tools/mlir/lib/CAPI/IR/CMakeFiles/obj.MLIRCAPIIR.dir/BuiltinAttributes.cpp.o
690.369 [1972/1/4849] Building CXX object tools/mlir/lib/CAPI/Transforms/CMakeFiles/obj.MLIRCAPITransforms.dir/Rewrite.cpp.o
690.433 [1971/1/4850] Building CXX object tools/mlir/test/lib/Conversion/VectorToSPIRV/CMakeFiles/MLIRTestVectorToSPIRV.dir/TestVectorReductionToSPIRVDotProd.cpp.o
690.485 [1970/1/4851] Building CXX object tools/mlir/tools/mlir-parser-fuzzer/bytecode/CMakeFiles/mlir-bytecode-parser-fuzzer.dir/DummyParserFuzzer.cpp.o
690.553 [1969/1/4852] Building CXX object tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestVisitors.cpp.o
706.363 [1968/1/4853] Building CXX object tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestVisitorsGeneric.cpp.o
FAILED: tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestVisitorsGeneric.cpp.o 
/usr/local/bin/c++ -DGTEST_HAS_RTTI=0 -DMLIR_INCLUDE_TESTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/build/tools/mlir/test/lib/IR -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/test/lib/IR -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/build/tools/mlir/include -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/include -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/build/include -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/llvm/include -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/test/lib/IR/../Dialect/Test -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/build/tools/mlir/test/lib/IR/../Dialect/Test -fPIC -fno-semantic-interposition -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 -Wundef -Werror=mismatched-tags -O3 -DNDEBUG -std=c++17  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestVisitorsGeneric.cpp.o -MF tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestVisitorsGeneric.cpp.o.d -o tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestVisitorsGeneric.cpp.o -c /home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/test/lib/IR/TestVisitorsGeneric.cpp
In file included from /home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/test/lib/IR/TestVisitorsGeneric.cpp:9:
/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/test/lib/IR/../Dialect/Test/TestOps.h:148:10: fatal error: 'TestOps.h.inc' file not found
  148 | #include "TestOps.h.inc"
      |          ^~~~~~~~~~~~~~~
1 error generated.
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/123411