Revert "Rollup merge of #97346 - JohnTitor:remove-back-compat-hacks, … …r=oli-obk" This reverts commitc703d11dcc, reversing changes made to64eb9ab869. it didn't apply cleanly, so now it works the same for RPIT and for TAIT instead of just working for RPIT, but we should keep those in sync anyway. It also exposed a TAIT bug (see the feature gated test that now ICEs). r? `@pnkfelix` fixes #99536