Reorganize Stat, Statx, and SockaddrStorage #4634

Job	Run time
Check --no-default-features (nightly)	56s
Check nightly-only targets (nightly)	22s
Check (stable)	5m 46s
Check selected Tier 3 platforms (nightly)	5m 1s
Check (nightly)	5m 50s
Rustfmt	3s
Check (1.63)	6m 2s
Test rustix_use_experimental_asm (powerpc64le-linux)	1m 16s
Test rustix_use_experimental_asm (s390x-linux)	1m 9s
Test (ubuntu)	44s
Test (ubuntu-20.04)	43s
Test use-libc (ubuntu)	40s
Test (i686-linux)	1m 5s
Test use-libc (i686-linux)	1m 15s
Test (aarch64-linux)	1m 11s
Test use-libc (aarch64-linux)	2m 5s
Test use-libc (powerpc64le-linux)	2m 7s
Test (powerpc64le-linux)	1m 28s
Test use-libc (riscv64-linux)	1m 5s
Test (riscv64-linux)	1m 18s
Test (s390x-linux)	1m 22s
Test use-libc (s390x-linux)	1m 52s
Test (arm-linux)	1m 11s
Test use-libc (arm-linux)	2m 51s
Test (ubuntu-stable)	48s
Test (i686-linux-stable)	2m 44s
Test (aarch64-linux-stable)	1m 13s
Test (riscv64-linux-stable)	1m 6s
Test (s390x-linux-stable)	1m 8s
Test (powerpc64le-linux-stable)	1m 11s
Test (arm-linux-stable)	1m 15s
Test (ubuntu-1.63)	2m 29s
Test (i686-linux-1.63)	3m 51s
Test (aarch64-linux-1.63)	3m 52s
Test (riscv64-linux-1.63)	2m 58s
Test (s390x-linux-1.63)	2m 56s
Test (powerpc64le-linux-1.63)	3m 28s
Test (arm-linux-1.63)	3m 5s
Test (macos-latest)	33s
Test (macos-13)	48s
Test (windows)	51s
Test (windows-2019)	1m 0s
Test (musl)	39s
	1h 23m 17s

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