Auto merge of #114534 - niluxv:strict_prov_unwind, r=cuviper,workingjubilee

Strict provenance unwind

1. Turned many `usize`s in the personality/unwind code that are actually pointers into `*const u8`.
2. Rewrote `read_encoded_pointer` to conform to strict-provenance, along the lines as described by `@eddyb` [in zulip some time ago](https://rust-lang.zulipchat.com/#narrow/stream/136281-t-opsem/topic/strict.20provenance.20in.20dwarf.3A.3Aeh/near/276197290).

This should make supporting CHERI in the future easier (but they use a [slightly modified format in the callsite table](https://cheri-compiler-explorer.cl.cam.ac.uk/z/n6GhhW), which requires a CHERI specific modification to `find_eh_action`).

Author: bors