Use custom traits instead of libstd's `MetadataExt` and `PermissionsExt`. #1634

Job	Run time
Check Cross-Compilation on Rust nightly on Windows (nightly)	1m 0s
Check Cross-Compilation on Windows (stable)	1m 9s
Check Cross-Compilation (stable)	43s
Check Cross-Compilation on Windows (beta)	1m 4s
Check Cross-Compilation on Rust nightly (nightly)	56s
Fuzz Targets	47s
Check Cross-Compilation (beta)	51s
Rustfmt	11s
Test linux-raw support (ubuntu)	23s
Test (stable)	10s
Test linux-raw support (ubuntu-20.04)	24s
Test (msrv)	1m 50s
Test on Musl (ubuntu)	34s
Test (windows-latest)	9s
Test (windows-2019)	12s
Test with Rust nightly (ubuntu)	25s
Test (macos-latest)	12s
Test with Rust nightly (windows)	27s
Test (macos-11)	11s
Test (beta)	21s
Test (ubuntu-20.04)	16s
Test (aarch64-ubuntu)	25s
	12m 40s

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