Test minimal dependency versions in CI #29

Job	Run time
Rustdoc	45s
Clippy	26s
Rustdoc with `cfg(docsrs)`	43s
Build	21s
Clippy (`tls-rustls`)	44s
Minimal Versions	1m 1s
Build (`tls-rustls`)	38s
Clippy (`tls-rustls-no-provider`)	23s
Minimal Versions (`tls-rustls`)	58s
Build (`tls-rustls-no-provider`)	27s
Clippy (`tls-openssl`)	26s
Rustfmt	11s
Minimal Versions (`tls-rustls-no-provider`)	1m 0s
Build (`tls-openssl`)	50s
Clippy (`--all-features`)	58s
Minimal Versions (`tls-openssl`)	4s
Build (`--all-features`)	45s
Minimal Versions (`--all-features`)	6s
Build MSRV	1m 2s
Test	1s
Build MSRV (`tls-rustls`)	1m 1s
Build MSRV (`tls-rustls-no-provider`)	58s
Test (`tls-rustls`)	24s
Build MSRV (`tls-openssl`)	1m 2s
Test (`rustls/ring`)	26s
Build MSRV (`--all-features`)	1m 1s
Test (`tls-openssl`)	15s
Test (`--all-features`)	19s
	17m 15s

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