[llvm] [NFC][TableGen] Emit nested namespaces in InstrInfoEmitter (PR #124210)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

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

Full details are available at: https://lab.llvm.org/buildbot/#/builders/50/builds/9365

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

```
Step 5 (build-unified-tree) failure: build (failure)
...
377.348 [1207/5/5609] Linking CXX static library lib/libMLIRShapeDialect.a
377.408 [1207/4/5610] Linking CXX static library lib/libMLIRBufferizationDialect.a
377.441 [1207/3/5611] Linking CXX static library lib/libMLIRSCFDialect.a
377.455 [1207/2/5612] Linking CXX static library lib/libMLIRShardingInterface.a
377.583 [1206/2/5613] Linking CXX static library lib/libMLIRLinalgDialect.a
377.671 [1198/9/5614] Linking CXX static library lib/libMLIRAffineAnalysis.a
377.683 [1198/8/5615] Linking CXX static library lib/libMLIRRewritePDL.a
377.691 [1198/7/5616] Linking CXX static library lib/libMLIRSparseTensorUtils.a
377.699 [1198/6/5617] Linking CXX static library lib/libMLIRVectorDialect.a
377.717 [1198/5/5618] 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.
377.746 [1198/4/5619] Linking CXX static library lib/libMLIRTensorUtils.a
377.752 [1198/3/5620] Linking CXX static library lib/libMLIRTensorMeshShardingExtensions.a
377.753 [1198/2/5621] Linking CXX static library lib/libMLIRTosaDialect.a
377.767 [1198/1/5622] Linking CXX static library lib/libMLIRFuncMeshShardingExtensions.a
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/124210