Reorganize sockopts code and add several more socket options #3302

Job	Run time
Check --no-default-features (nightly)	1m 31s
Check selected Tier 3 platforms (nightly)	57s
Check (stable)	4m 17s
Check nightly-only targets (nightly)	42s
Rustfmt	20s
Check (nightly)	4m 24s
Check (1.63)	4m 33s
Test rustix_use_experimental_asm (powerpc64le-linux)	1m 54s
Test use-libc (ubuntu)	1m 19s
Test use-libc (i686-linux)	1m 29s
Test use-libc (aarch64-linux)	1m 57s
Test use-libc (powerpc64le-linux)	1m 49s
Test (ubuntu)	1m 3s
Test use-libc (riscv64-linux)	1m 39s
Test (ubuntu-20.04)	1m 11s
Test use-libc (arm-linux)	2m 56s
Test (i686-linux)	56s
Test (aarch64-linux)	1m 8s
Test (powerpc64le-linux)	1m 12s
Test (riscv64-linux)	1m 7s
Test (s390x-linux)	1m 7s
Test (arm-linux)	1m 9s
Test (ubuntu-stable)	57s
Test (i686-linux-stable)	51s
Test (aarch64-linux-stable)	1m 11s
Test (riscv64-linux-stable)	1m 7s
Test (s390x-linux-stable)	1m 9s
Test (powerpc64le-linux-stable)	58s
Test (arm-linux-stable)	1m 10s
Test (ubuntu-1.63)	1m 7s
Test (i686-linux-1.63)	1m 7s
Test (aarch64-linux-1.63)	1m 0s
Test (riscv64-linux-1.63)	1m 7s
Test (s390x-linux-1.63)	1m 6s
Test (powerpc64le-linux-1.63)	1m 8s
Test (arm-linux-1.63)	1m 9s
Test (macos-latest)	1m 8s
Test (macos-11)	1m 8s
Test (windows)	55s
Test (windows-2019)	54s
	57m 52s

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