Rollup merge of #97557 - compiler-errors:arg-mismatch-mini, r=jackh726

Rollup merge of #97557 - compiler-errors:arg-mismatch-mini, r=jackh726

Fix indices and remove some unwraps in arg mismatch algorithm

This is a more conservative fix than #97542, addressing some indices which were used incorectly and unwraps which are bound to panic (e.g. when the provided and expected arg counts differ). Beta nominating this as it's quite easy to cause ICEs -- I wrote a fuzzer and found hundreds of examples of ICEs.

cc `@jackh726` as author of #92364, and `@estebank` as reviewer of that PR.
fixes #97484
r? `@jackh726` this should be _much_ easier to review than the other PR :sweat_smile: