Auto merge of #114914 - compiler-errors:deduce-tait-in-future-output,…

… r=lcnr

Normalize return type of `deduce_future_output_from_obligations`

Fixes #114909
Also confirmed to fix #114727 manually

Now that we have weak/lazy type aliases, we need to normalize those in future signatures to ensure that `replace_opaque_types_with_inference_vars` actually sees TAITs behind them. This isn't needed in the new solver, but added a test to make sure it doesn't regress there either.

r? types cc `@oli-obk` (who's gone, worst case can delay this PR until he's back)