[songgaoye]

What problem does this PR solve?

Issue Number: resolve

Problem Summary:

• bthread_id accesses butex state words as plain uint32_t values even though butex manages them as atomic state. Concurrent bthread_id_join() and bthread_id_unlock_and_destroy() can therefore form a C++ data race.
  What is changed and the side effects?

Changed:

• Store ID butex state as butil::atomic.
• Centralize atomic version-word access helpers.
• Add a concurrent join/destroy regression test.

Side effects:

• Performance effects:

• Breaking backward compatibility:

---

Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[songgaoye]

run tsan on master branch.

Running main() from /tmp/brpc-master-tsan/build-tsan/googletest-src/googletest/src/gtest_main.cc
Note: Google Test filter = BthreadIdTest.join_races_with_destroy
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from BthreadIdTest
[ RUN      ] BthreadIdTest.join_races_with_destroy
==================
WARNING: ThreadSanitizer: data race (pid=344302)
  Write of size 4 at 0x729400000040 by main thread:
    #0 bthread_id_unlock_and_destroy /tmp/brpc-master-tsan/src/bthread/id.cpp:630
    #1 TestBody /tmp/brpc-master-tsan/test/bthread_id_unittest.cpp:143
    #2 testing::Test::Run()
    #3 testing::TestInfo::Run()
    #4 testing::TestSuite::Run()
    #5 testing::internal::UnitTestImpl::RunAllTests()
    #6 testing::UnitTest::Run()
    #7 RUN_ALL_TESTS()
    #8 main

  Previous atomic read of size 4 at 0x729400000040 by thread T2:
    #0 std::__atomic_base<int>::load(std::memory_order)
    #1 bthread::butex_wait(void*, int, timespec const*, bool)
       /tmp/brpc-master-tsan/src/bthread/butex.cpp:755
    #2 bthread_id_join
       /tmp/brpc-master-tsan/src/bthread/id.cpp:530
    #3 join_race_waiter
       /tmp/brpc-master-tsan/test/bthread_id_unittest.cpp:125

  Thread T2 created by main thread at:
    #0 pthread_create
    #1 TestBody /tmp/brpc-master-tsan/test/bthread_id_unittest.cpp:137

SUMMARY: ThreadSanitizer: data race
  /tmp/brpc-master-tsan/src/bthread/id.cpp:630
  in bthread_id_unlock_and_destroy
==================
[       OK ] BthreadIdTest.join_races_with_destroy (260 ms)
[----------] 1 test from BthreadIdTest (260 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test suite ran. (260 ms total)
[  PASSED  ] 1 test.
ThreadSanitizer: reported 1 warnings
EXIT_CODE=66