[BUILD] Fix multiple assignment operators for SpinLockMutex #9065

Job	Run time
Bazel asan config	14m 44s
Bazel noexcept	12m 14s
Bazel nortti	12m 30s
Bazel on MacOS	37m 32s
Bazel	12m 47s
Bazel with async export	12m 53s
Bazel tsan config	13m 18s
Bazel with external abseil	12m 45s
Bazel valgrind	14m 10s
Benchmark	8m 8s
CMake test (with abseil)	4m 38s
CMake clang 14 (maintainer mode, abiv2)	13m 56s
CMake clang 14 (maintainer mode, async)	15m 6s
CMake clang 14 (maintainer mode, sync)	15m 43s
CMake do not install test (with otlp-exporter)	14m 12s
CMake gcc 12 (maintainer mode, sync)	7m 46s
CMake gcc 12 (maintainer mode, async)	8m 11s
CMake install test (with abseil)	4m 25s
CMake test (with modern protobuf,grpc and abseil)	18m 50s
CMake msvc (maintainer mode)	8m 49s
CMake msvc (maintainer mode) with C++20	9m 7s
CMake test (with opentracing-shim)	4m 12s
CMake test (build shared libraries with otlp-exporter and static gRPC)	13m 46s
CMake test (without otlp-exporter)	4m 55s
CMake test (with otlp-exporter)	14m 8s
CMake C++17 test(GCC)	4m 33s
CMake C++14 test(GCC)	4m 5s
CMake C++20 test(Clang with libc++)	9m 17s
CMake C++20 test(GCC)	8m 18s
CMake test (without otlp-exporter and with async export)	4m 47s
Code coverage	11m 49s
Copyright	4s
DocFX check	42s
markdown-lint	6s
Format	13s
misspell	6s
Plugin -> CMake	57s
CMake -> exporter proto	12m 51s
Bazel Windows	21m 54s
Plugin -> CMake Windows	6m 34s
CMake (With async export) -> exporter proto	12m 49s
CMake -> exporter proto (Build as DLL)	18m 50s
	7h 6m 40s

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