Introduce set_custom_verify_callback and set_async_custom_verify_callback #645

Job	Run time
Test FIPS integration	1m 55s
clippy	1m 36s
Cross build from macOS to Linux (x86_64-unknown-linux-gnu)	4m 5s
Cross build from macOS to Linux (FIPS) (x86_64-unknown-linux-gnu)	4m 32s
rustfmt	23s
Test features	3m 16s
Test (stable)	2m 8s
Test (macos-x86_64)	3m 5s
Test (arm-android)	2m 12s
Test (arm64-android)	2m 7s
Test (i686-android)	3m 55s
Test (x86_64-android)	2m 6s
Test (aarch64-ios)	5m 8s
Test (aarch64-ios-sim)	3m 48s
Test (x86_64-ios)	5m 15s
Test (i686-linux)	2m 1s
Test (arm-linux)	2m 1s
Test (aarch64-linux)	2m 15s
Test (x86_64-musl)	2m 4s
Test (x86_64-mingw)	2m 4s
Test (i686-msvc)	6m 10s
Test (x86_64-msvc)	4m 41s
	1h 6m 47s

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