Add sendmmsg support for UDP #147

Job	Run time
build-test-sanitizer-address	3m 11s
cppcheck-test	7m 36s
build-test-ubuntu-ish (ubuntu-latest)	3m 28s
build-test-ubuntu-ish (ubuntu-22.04-arm)	3m 47s
build-test-macos-ish (macos-14)	2m 28s
build-test-macos-ish (macos-15)	3m 12s
build-test-ubuntu-ish (ubuntu-22.04)	2m 59s
	26m 41s

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