Use custom traits instead of libstd's `MetadataExt` and `PermissionsExt`. #1636

Job	Run time
Rustfmt	12s
Check Cross-Compilation on Windows (stable)	49s
Check Cross-Compilation on Windows (beta)	46s
Check Cross-Compilation on Rust nightly (nightly)	1m 54s
Check Cross-Compilation on Rust nightly on Windows (nightly)	55s
Check Cross-Compilation (stable)	1m 19s
Check Cross-Compilation (beta)	1m 21s
Test on Musl (ubuntu)	45s
Test (stable)	24s
Test with Rust nightly (ubuntu)	29s
Test (windows-latest)	1m 4s
Test with Rust nightly (windows)	42s
Fuzz Targets	47s
Test (windows-2019)	1m 0s
Test (macos-latest)	1m 4s
Test (msrv)	2m 22s
Test linux-raw support (ubuntu)	33s
Test linux-raw support (ubuntu-20.04)	29s
Test (macos-11)	1m 7s
Test (beta)	31s
Test (ubuntu-20.04)	30s
Test (aarch64-ubuntu)	1m 19s
	20m 22s

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