Rollup merge of #146711 - lcnr:fix-placeholder-ice, r=lqd

fix 2 borrowck issues

fixes rust-lang/rust#146467 cc ``@amandasystems``

our understanding here is as follows: region constraints from computing implied bounds gets `ConstraintCategory::Internal`. If there's a higher-ranked subtyping errors while computing implied bounds we then ended up with only `ConstraintCategory::Internal` and `ConstraintCategory::OutlivesUnnameablePlaceholder(_)` constraints.

The path was something like
- `'placeholderU2: 'placeholderU1` (`Internal`)
- `'placeholderU1: 'static` (`OutlivesUnnameablePlaceholder('placeholderU2)`)

It's generally somewhat subtle here as ideally relating placeholders doesn't introduce `'static` constraints. Relating the placeholders themselves will always error regardless, cc rust-lang/rust#142623.

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separately fixes rust-lang/rust#145925 (comment) by updating the location for deferred closure requirements inside of promoteds. I am not updating their category as doing so is 1) effort and 2) imo actually undesirable 🤔 see the comments in `TypeChecker::check_promoted` cc ``@lqd``

r? lqd

Author: matthiaskrgr