Omer, Ben

There’s a little cluster of tickets that it’d be really good to nail.

• !1381/#16893: inline unsafeCoerce# in CorePrep
• #17041: coercion safety in STG Lint
• !1552: tidy up linting on unsafe coercions
• #16964: definition of Int#
• #17026: definition of IntRep

They are all somehow tied up together.  Can we kill them off together, soon?  I have left comments...

Simon