[clang] [clang] Be const-correct with all uses of `Module *`. (PR #93493)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

You don't have to convince me that being const-correct is a good thing, I'm already in full support of that. :-)

The push back isn't "no, don't do this", it's "we're not const correct in a *lot* of places and so adding const correctness to a part of the compiler without considering the bigger picture means increasing the chances of needing to add `const_cast` in places to avoid viral changes in the future."

https://github.com/llvm/llvm-project/pull/93493