Auto merge of #88098 - Amanieu:oom_panic, r=nagisa

Implement -Z oom=panic

This PR removes the `#[rustc_allocator_nounwind]` attribute on `alloc_error_handler` which allows it to unwind with a panic instead of always aborting. This is then used to implement `-Z oom=panic` as per RFC 2116 (tracking issue #43596).

Perf and binary size tests show negligible impact.