meson: Add Meson build system #1

Job	Run time
basic_gcc	6m 46s
basic_clang	4m 26s
check_docs	1m 12s
check_update	56s
check-ansi	3m 18s
minimal	4m 8s
address_ub_sanitizer	15m 33s
buildtest	5m 55s
enable_non-default_options	3m 26s
external-tests	3m 23s
external-test-pyca (1.51.0, 3.9)	1m 33s
fips_and_ktls	4m 29s
legacy	5m 54s
memory_sanitizer	23m 21s
no-deprecated	6m 19s
no-legacy	6m 35s
non-caching	10m 15s
no-shared (ubuntu-latest)	6m 42s
no-shared (macos-latest)	7m 32s
threads_sanitizer	5m 49s
out-of-source-and-install (ubuntu-latest)	6m 1s
out-of-source-and-install (macos-latest)	7m 47s
	2h 21m 20s

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