[ARM] Add extra extend and trunc costs for cast instructions

This expands the existing extend costs with a few extras for larger
types than legal, which will usually be split under MVE. It also adds
trunk support for the same thing. These should not have a large effect
on many things, but makes the costs explicit and keeps a certain balance
between the trunks and extends.

Differential Revision: https://reviews.llvm.org/D82457