[SEMANTIC CONVENTIONS] Upgrade to 1.21.0 (#2248) #8307

Job	Run time
Bazel noexcept	24m 56s
Bazel asan config	29m 24s
Bazel nortti	18m 52s
Bazel on MacOS	26m 48s
Bazel	19m 24s
Bazel with async export	20m 16s
Bazel tsan config	27m 46s
Bazel valgrind	22m 2s
Bazel with external abseil	27m 56s
Benchmark	14m 32s
CMake test (with abseil)	7m 10s
CMake clang 14 (maintainer mode, async)	30m 37s
CMake clang 14 (maintainer mode, sync)	20m 58s
CMake do not install test (with otlp-exporter)	19m 8s
CMake gcc 4.8 (with otlp exporter)	16m 9s
CMake gcc 4.8 (without otlp exporter)	5m 49s
CMake gcc 12 (maintainer mode, async)	15m 55s
CMake gcc 12 (maintainer mode, C++11, async)	16m 54s
CMake gcc 12 (maintainer mode, sync)	21m 56s
CMake msvc (maintainer mode)	10m 41s
CMake test (with opentracing-shim)	5m 52s
CMake test (build shared libraries with otlp-exporter and static gRPC)	18m 36s
CMake test (with otlp-exporter)	24m 17s
CMake test (without otlp-exporter)	6m 43s
CMake C++20 test(Clang with libc++)	12m 10s
CMake C++20 test(GCC)	10m 48s
CMake test (without otlp-exporter and with async export)	6m 35s
Code coverage	12m 19s
Copyright	8s
DocFX check	1m 5s
Format	19s
markdown-lint	6s
misspell	4s
Plugin -> CMake	1m 14s
CMake -> exporter proto	17m 13s
Bazel Windows	48m 28s
Plugin -> CMake Windows	8m 40s
CMake (With async export) -> exporter proto	16m 52s
CMake -> exporter proto (Build as DLL)	16m 42s
	10h 5m 24s

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