Split os_utils into a submodule #6364

Job	Run time
Windows (shared, x86_64, windows-2022)	22m 45s
Windows (static, x86_64, windows-2022)	16m 32s
Windows (amalgamation, x86_64, windows-2022)	12m 48s
Windows (shared, x86, windows-2022)	23m 11s
Clang Tidy	3m 32s
Linux (gcc, shared)	3m 11s
Linux (gcc, amalgamation)	4m 31s
macOS (shared, xcode, macos-13)	6m 57s
macOS (amalgamation, xcode, macos-13)	6m 49s
Linux (gcc, static)	2m 33s
macOS (shared, xcode, macos-14)	2m 27s
Linux (clang, shared)	3m 1s
macOS (amalgamation, xcode, macos-14)	1m 33s
Analysis (coverage, gcc, ubuntu-24.04)	31m 23s
Special (examples, gcc, ubuntu-24.04)	2m 38s
Analysis (sanitizer, clang, ubuntu-24.04)	32m 27s
Special (minimized, gcc, ubuntu-24.04)	48s
Analysis (valgrind, clang, ubuntu-24.04)	46m 55s
Special (bsi, gcc, ubuntu-24.04)	2m 44s
Analysis (fuzzers, gcc, ubuntu-24.04)	18m 28s
Cross (cross-i386, gcc, ubuntu-22.04)	4m 45s
Special (docs, gcc, ubuntu-24.04)	1m 5s
Analysis (lint, gcc, ubuntu-24.04)	1m 6s
Special (no_pcurves, gcc, ubuntu-24.04)	3m 3s
Cross (cross-arm32, gcc, ubuntu-24.04)	15m 15s
Analysis (format, gcc, ubuntu-24.04)	42s
Cross (cross-arm64, gcc, ubuntu-24.04)	7m 58s
Analysis (limbo, gcc, ubuntu-24.04)	2m 21s
Cross (cross-ppc64, gcc, ubuntu-24.04)	9m 29s
Cross (cross-mips64, gcc, ubuntu-24.04)	9m 43s
Cross (cross-android-arm64, clang, ubuntu-24.04)	5m 46s
Cross (static, gcc, windows-2022, make)	4m 45s
Cross (cross-ios-arm64, xcode, macos-13)	2m 36s
	5h 13m 47s

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