Rollup merge of #87645 - LeSeulArtichaut:issue-87414, r=oli-obk

Properly find owner of closure in THIR unsafeck

Previously, when encountering a closure in a constant, the THIR unsafeck gets invoked on the owner of the constant instead of the constant itself, producing cycles.
Supersedes #87492. ```@FabianWolff``` thanks for your work on that PR, I copied your test file and added you as a co-author.

Fixes #87414.
r? ```@oli-obk```