Rollup merge of #108754 - compiler-errors:retry, r=oli-obk

Retry `pred_known_to_hold_modulo_regions` with fulfillment if ambiguous

Fixes #108721

The problem here is that when we're checking `is_sized_raw` during codegen on some type that has a lot of opaques in it, something emits several nested obligations that are individually ambiguous, but when processed together in a loop then apply modulo regions. Since the `evaluate_predicates_recursively` inner loop doesn't process predicates until they stop changing, we return `EvaluatedToAmbig`, which makes the sized check return false incorrectly. See:

https://github.com/rust-lang/rust/blob/f15f0ea73972786e426732c5b92ba9a904b866c4/compiler/rustc_trait_selection/src/traits/select/mod.rs#L596-L606

... Compared to the analogous loop in the new solver:

https://github.com/rust-lang/rust/blob/f15f0ea73972786e426732c5b92ba9a904b866c4/compiler/rustc_trait_selection/src/solve/mod.rs#L481-L512

To fix this, if we get ambiguous during `pred_known_to_hold_modulo_regions`, just retry the obligation in a fulfillment context.

--

Unfortunately... I don't have a test for this. I've only tested this locally. Pending minimization :/

r? types

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