Rollup merge of #147533 - cjgillot:coro-late-renumber, r=davidtwco

Renumber return local after state transform

The current implementation of `StateTransform` renames `_0` before analyzing liveness. This is inconsistent, as a `return` terminator hardcodes a read of `_0`.

This PR proposes to perform such rename *after* analyzing the body, in fact after the whole transform. The implementation is not much more complicated.

Author: matthiaskrgr