expose `Cr3::write_raw` #2825

Job	Run time
Bootloader Integration Test (ubuntu-latest)	1m 23s
Bootloader Integration Test (macos-latest)	1m 58s
Bootloader Integration Test (windows-latest)	4m 48s
Clippy	15s
Check Formatting	15s
Semver Checks	29s
Test MSRV and Stable Features (nightly)	20s
Test MSRV and Stable Features (1.59)	2m 7s
Test (ubuntu-latest)	33s
Test MSRV and Stable Features (1.57)	2m 9s
Test (macos-latest)	1m 2s
Test (windows-latest)	57s
	16m 16s

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