Rollup merge of #101690 - kadiwa4:avoid_iterator_last, r=oli-obk

Avoid `Iterator::last`

Adapters like `Filter` and `Map` use the default implementation of `Iterator::last` which is not short-circuiting (and so does `core::str::Split`). The predicate function will be run for every single item of the underlying iterator. I hope that removing those calls to `last` results in slight performance improvements.

diff --cc compiler/rustc_hir/src/hir.rs
Simple merge