Avoid mkTick in Core Prep breaking ANF

sheafrequested to merge
sheaf/ghc:T27182 into master

Ticket: #27182 (closed).

This MR implements a stop-gap measure to fix the bug in #27182 (closed), pending a deeper refactor of mkTick as per #27141.

The ticket shows that mkTick can break ANF. Most calls to mkTick in Core Prep are actually safe, except for one, which this patch changes to Tick. The other calls are now wrapped with an assertion that ensures ANF is not broken.

See Note [mkTick breaks ANF] in GHC.CoreToStg.Prep.

Edited by sheaf

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