Auto merge of #108691 - aliemjay:closure-subject, r=jackh726

fix multiple issues when promoting type-test subject

Multiple interdependent fixes.  See linked issues for a short description of each.

When Promoting a type-test `T: 'a` from within the closure back to its parent function, there are a couple pre-existing bugs and limitations. They were exposed by the recent changes to opaque types because the type-test subject (`T`) is no longer a simple ParamTy.

Commit 1:
Fixes #108635
Fixes #107426

Commit 2:
Fixes #108639

Commit 3:
Fixes #107516

Author: bors