Rollup merge of #88270 - lqd:hrtb-type-ascription, r=nikomatsakis
Handle type ascription type ops in NLL HRTB diagnostics
Currently, there are still a few cases of the "higher-ranked subtype error" of yore, 4 of which are related to type ascription.
This PR is a follow-up to #86700, adding support for type ascription type ops, and makes 3 of these tests output the same diagnostics in NLL mode as the migrate mode (and 1 is now much closer, especially if you ignore that it already outputs an additional error in NLL mode -- which could be a duplicate caused by a lack of normalization like [these comments point out](9583fd1bdd/compiler/rustc_traits/src/type_op.rs (L122-L157)), or an imprecision in some parts of normalization as [described here](https://github.com/rust-lang/rust/pull/86700#discussion_r689086688)).
Since we discussed these recently:
- [here](https://github.com/rust-lang/rust/pull/86700#discussion_r689158868), cc ````@matthewjasper,````
- and [here](https://github.com/rust-lang/rust/issues/57374#issuecomment-901500856), cc ````@Aaron1011.````
It should only leave [this TAIT test](9583fd1bdd/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.rs) as still emitting [the terse error](9583fd1bdd/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.nll.stderr).
r? ````@estebank```` (so that they shake their fist at NLL's general direction less often) or ````@nikomatsakis```` or matthew or aaron, the more the merrier.
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