src,lib: implement experimental DTLS API #6603

Job	Run time
Build slim tarball	1m 10s
aarch64-linux: Cache V8 build	1h 5m 10s
x86_64-darwin: with shared libraries	3h 0m 24s
aarch64-darwin: with shared libraries	2h 10m 38s
x86_64-linux: with shared libraries	2h 4m 52s
aarch64-linux: with shared openssl-1.1.1w	26m 11s
aarch64-linux: with shared openssl-3.5.5	26m 28s
aarch64-linux: with shared openssl-3.0.19	26m 27s
aarch64-linux: with shared openssl-3.6.1	26m 32s
aarch64-linux: with shared boringssl-0.20260413.0	26m 18s
aarch64-linux: with shared openssl-4.0.0	26m 50s
	11h 1m 0s

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