Linux

Update libdatachannel to v0.21.2 #3099

Job	Run time
check headers	4m 30s
build (asio-debugging=on picker-debugging=on)	4m 31s
build (extensions=off logging=off streaming=off super-seeding=off share-mode=off predictive-piece...	3m 40s
build (crypto=gcrypt)	3m 35s
clang-tidy	10m 10s
build (mmap-disk-io=off)	4m 8s
build dist (ubuntu-20.04)	3m 4s
Fuzzers	15m 58s
build dist (ubuntu-22.04)	2m 21s
pre-commit	25s
Simulations	8m 17s
Tests (webtorrent=on address-sanitizer=norecover undefined-sanitizer=norecover crypto=openssl)	6m 19s
Tests (toolset=clang logging=off address-sanitizer=norecover undefined-sanitizer=norecover)	11m 58s
Tests (thread-sanitizer=norecover crypto=openssl release debug-symbols=on cxxflags=-Wno-tsan)	5m 11s
Tests (crypto=gnutls)	4m 58s
Tests (deprecated-functions=off)	4m 32s
	1h 33m 37s

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