Implement `chmod` and `fchmod` for Unix targets #10098

Job	Run time
build (ubuntu-latest, x86_64-unknown-linux-gnu)	24m 20s
coverage report	6m 9s
build (macos-14, aarch64-apple-darwin)	28m 41s
style checks	2m 38s
build (windows-latest, i686-pc-windows-msvc)	26m 3s
conclusion	1s
cronjob failure notification	0s
	1h 27m 52s

Provide feedback