Rollup of 8 pull requests

[fmease]

Successful merges:

• Align: add bytes_usize and bits_usize #124579 (Align: add bytes_usize and bits_usize)
• Describe and use CStr literals in CStr and CString docs #124593 (Describe and use CStr literals in CStr and CString docs)
• run-make-support: preserve tooks.mk behavior for EXTRACXXFLAGS #124594 (run-make-support: preserve tooks.mk behavior for EXTRACXXFLAGS)
• library/std: Remove unused gimli-symbolize feature #124604 (library/std: Remove unused gimli-symbolize feature)
• rustc_expand cleanups #124607 (rustc_expand cleanups)
• variable-precision float operations can differ depending on optimization levels #124609 (variable-precision float operations can differ depending on optimization levels)
• Tweak consts_may_unify #124610 (Tweak consts_may_unify)
• shallow resolve in orphan check #124623 (shallow resolve in orphan check)

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