Rollup merge of #106322 - compiler-errors:CollectAllMismatches-infer-vars, r=oli-obk

Handle inference variables in `CollectAllMismatches` correctly

1. Fix #106240
2. Treat int/float type variables correctly (see `src/test/ui/iterators/invalid-iterator-chain-with-int-infer.rs`), so we can point out things like "`Iterator::Item` changed to `{integer}` here"

Author: Noratrieb