Auto merge of #122387 - DianQK:re-enable-early-otherwise-branch, r=cjgillot

Re-enable the early otherwise branch optimization

Closes #95162. Fixes #119014.

This is the first part of #121397.

An invalid enum discriminant can come from anywhere. We have to check to see if all successors contain the discriminant statement. This should have a pass to hoist instructions.

r? cjgillot

Author: bors