Use custom traits instead of libstd's `MetadataExt` and `PermissionsExt`. #1638

Job	Run time
Check Cross-Compilation on Rust nightly on Windows (nightly)	1m 50s
Check Cross-Compilation on Rust nightly (nightly)	1m 50s
Check Cross-Compilation (stable)	1m 8s
Check Cross-Compilation on Windows (stable)	3m 20s
Check Cross-Compilation (beta)	1m 29s
Check Cross-Compilation on Windows (beta)	1m 37s
Rustfmt	7s
Fuzz Targets	47s
Test (stable)	24s
Test (msrv)	2m 4s
Test (windows-latest)	1m 26s
Test linux-raw support (ubuntu)	31s
Test (windows-2019)	3m 27s
Test on Musl (ubuntu)	34s
Test linux-raw support (ubuntu-20.04)	30s
Test with Rust nightly (ubuntu)	32s
Test (macos-latest)	1m 0s
Test with Rust nightly (windows)	1m 28s
Test (macos-11)	1m 6s
Test (beta)	31s
Test (ubuntu-20.04)	27s
Test (aarch64-ubuntu)	2m 21s
	28m 29s

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