[SEMANTIC CONVENTIONS] Upgrade to 1.21.0 (#2248) #523

Job	Run time
CMake test (with abseil)	8m 38s
CMake clang 14 (maintainer mode, async)	20m 33s
CMake clang 14 (maintainer mode, sync)	27m 38s
CMake gcc 4.8 (with otlp exporter)	13m 22s
CMake gcc 4.8 (without otlp exporter)	4m 58s
CMake gcc 12 (maintainer mode, async)	21m 12s
CMake gcc 12 (maintainer mode, sync)	16m 2s
CMake msvc (maintainer mode)	9m 6s
CMake test (with opentracing-shim)	6m 21s
CMake gcc 12 (maintainer mode, C++11, async)	16m 39s
CMake test (without otlp-exporter)	6m 41s
CMake C++20 test(GCC)	13m 45s
CMake test (without otlp-exporter and with async export)	6m 36s
Bazel asan config	4m 51s
Bazel noexcept	2m 48s
Bazel nortti	3m 15s
Bazel on MacOS	5m 47s
Bazel	3m 16s
Bazel with async export	19m 40s
Bazel tsan config	3m 37s
Bazel valgrind	7m 14s
Bazel with external abseil	15m 17s
Benchmark	1m 26s
CMake do not install test (with otlp-exporter)	19m 9s
CMake test (build shared libraries with otlp-exporter and static gRPC)	26m 6s
CMake test (with otlp-exporter)	19m 18s
CMake C++20 test(Clang with libc++)	10m 34s
Code coverage	17m 9s
Copyright	7s
DocFX check	2m 8s
Format	17s
markdown-lint	10s
misspell	6s
Plugin -> CMake	1m 20s
CMake -> exporter proto	16m 23s
Bazel Windows	33m 33s
Plugin -> CMake Windows	8m 56s
CMake (With async export) -> exporter proto	16m 30s
CMake -> exporter proto (Build as DLL)	20m 16s
	7h 10m 44s

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