Rollup merge of #144936 - rcvalle:rust-cfi-fix-144641, r=lcnr

CFI: Fix types that implement Fn, FnMut, or FnOnce

When looking for instances which could either be dynamically called through a vtable or through a concrete trait method, we missed `FnPtrShim`, instead only looking at `Item` and closure-likes. Fixes rust-lang/rust#144641.

cc ```@1c3t3a``` ```@Jakob-Koschel```

Author: Zalathar