[clang] [hexagon] Add {con, de}structive interference size defn (PR #94877)

[Brian Cain via cfe-commits]

androm3da wrote:

> LGTM as far as the code goes, but please add some test coverage for the changes.

Not sure why I omitted it -- thanks.  Fixed.  

https://github.com/llvm/llvm-project/pull/94877