Restart inference of foreach nested functions when lowering returns

[limepoutine]

Fixes #22666, also fixes #22639. Also fixes Bugzilla 19408.

I'm turning a trivial bug fix into a big feature again. This PR restarts inference when lowering returns inside a foreach, commits when returns are rewritten, and runs semantic on opApply calls. Not particularly maintainable because we now need to patch lowering of foreach in semantic3. Contains pattern matching on lowered ASTs, speculative inference, and a reinvented wheel of counting sort.

This is not quite "full inference" yet, but quite compliant to the specs. Less compliant yet more lightweight are #22642 and #22672.

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Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#22685"

[limepoutine]

The buildkite failure is a true positive. PR: vibe-d/vibe-core#445