[llvm] [EquivClasses] Introduce members iterator-helper (PR #130139)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-x86_64-linux-abi-test` running on `sie-linux-worker2` while building `llvm` at step 6 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/8/builds/12188

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

```
Step 6 (build-unified-tree) failure: build (failure)
...
4.593 [6068/10/1015] Building CXX object third-party/benchmark/src/CMakeFiles/benchmark.dir/reporter.cc.o
4.603 [6067/10/1016] Building CXX object third-party/benchmark/src/CMakeFiles/benchmark.dir/statistics.cc.o
4.606 [6066/10/1017] Building CXX object third-party/benchmark/src/CMakeFiles/benchmark.dir/string_util.cc.o
4.625 [6065/10/1018] Building CXX object third-party/benchmark/src/CMakeFiles/benchmark.dir/sysinfo.cc.o
4.628 [6065/9/1019] Building CXX object third-party/benchmark/src/CMakeFiles/benchmark.dir/timers.cc.o
4.630 [6064/9/1020] Building CXX object third-party/benchmark/src/CMakeFiles/benchmark_main.dir/benchmark_main.cc.o
4.660 [6064/8/1021] Linking CXX static library lib/libbenchmark.a
4.669 [6063/8/1022] Linking CXX static library lib/libbenchmark_main.a
4.742 [6063/7/1023] Building AArch64TargetParserDef.inc...
5.801 [6062/7/1024] Building CXX object unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o
FAILED: unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o 
/opt/ccache/bin/g++ -DGTEST_HAS_RTTI=0 -DLLVM_BUILD_STATIC -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbot/buildbot-root/abi-test/build/unittests/ADT -I/home/buildbot/buildbot-root/abi-test/llvm/llvm/unittests/ADT -I/home/buildbot/buildbot-root/abi-test/build/include -I/home/buildbot/buildbot-root/abi-test/llvm/llvm/include -I/home/buildbot/buildbot-root/abi-test/llvm/third-party/unittest/googletest/include -I/home/buildbot/buildbot-root/abi-test/llvm/third-party/unittest/googlemock/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -fno-lifetime-dse -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -Wno-dangling-else -Wno-variadic-macros -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -Wno-suggest-override -std=c++17 -MD -MT unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o -MF unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o.d -o unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o -c /home/buildbot/buildbot-root/abi-test/llvm/llvm/unittests/ADT/EquivalenceClassesTest.cpp
In file included from /home/buildbot/buildbot-root/abi-test/llvm/third-party/unittest/googlemock/include/gmock/gmock.h:61,
                 from /home/buildbot/buildbot-root/abi-test/llvm/llvm/unittests/ADT/EquivalenceClassesTest.cpp:10:
/home/buildbot/buildbot-root/abi-test/llvm/third-party/unittest/googlemock/include/gmock/gmock-more-matchers.h: In instantiation of ‘bool testing::internal::IsEmptyMatcher::MatchAndExplain(const MatcheeContainerType&, testing::MatchResultListener*) const [with MatcheeContainerType = llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator>]’:
/home/buildbot/buildbot-root/abi-test/llvm/third-party/unittest/googletest/include/gtest/gtest-matchers.h:647:35:   required from ‘bool testing::PolymorphicMatcher<Impl>::MonomorphicImpl<T>::MatchAndExplain(T, testing::MatchResultListener*) const [with T = const llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator>&; Impl = testing::internal::IsEmptyMatcher]’
/home/buildbot/buildbot-root/abi-test/llvm/third-party/unittest/googletest/include/gtest/gtest-matchers.h:646:10:   required from here
/home/buildbot/buildbot-root/abi-test/llvm/third-party/unittest/googlemock/include/gmock/gmock-more-matchers.h:73:40: error: ‘const class llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator>’ has no member named ‘size’
   73 |     *listener << "whose size is " << c.size();
      |                                      ~~^~~~
7.413 [6062/6/1025] Building RISCVTargetParserDef.inc...
9.343 [6062/5/1026] Building CXX object unittests/Passes/Plugins/TestPlugin/CMakeFiles/TestPlugin.dir/TestPlugin.cpp.o
9.620 [6062/4/1027] Building CXX object unittests/Analysis/InlineAdvisorPlugin/CMakeFiles/InlineAdvisorPlugin.dir/InlineAdvisorPlugin.cpp.o
10.324 [6062/3/1028] Building CXX object unittests/Analysis/InlineOrderPlugin/CMakeFiles/InlineOrderPlugin.dir/InlineOrderPlugin.cpp.o
10.329 [6062/2/1029] Building CXX object unittests/Passes/Plugins/DoublerPlugin/CMakeFiles/DoublerPlugin.dir/DoublerPlugin.cpp.o
11.872 [6062/1/1030] Building CXX object utils/TableGen/CMakeFiles/llvm-tblgen.dir/GlobalISelCombinerEmitter.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/130139