[clang] [Clang][CodeGen] Start migrating away from assuming the Default AS is 0 (PR #88182)

[Alex Voicu via cfe-commits]

https://github.com/AlexVlx commented:

> This adds a third copy of the same test, can we just merge them add add three RUN lines with different CHECK prefixes? 

I've merged the address-space related ones, but I've left the basic one in place.

https://github.com/llvm/llvm-project/pull/88182