chore: prepare release 0.21.0 (#1041) #1366

Job	Run time
test (ubuntu-latest)	18m 5s
Build x86_64-unknown-linux-musl	13m 10s
test (macos-latest)	14m 6s
Build aarch64-unknown-linux-musl	13m 10s
test (windows-latest)	28m 43s
Build powerpc64le-unknown-linux-gnu	14m 4s
Build x86_64-apple-darwin	22m 17s
Build aarch64-apple-darwin	14m 15s
Build x86_64-pc-windows-gnu	22m 16s
Build x86_64-pc-windows-msvc	22m 16s
Post-process	3s
	3h 2m 25s

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