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

[David Stone via cfe-commits]

davidstone wrote:

> Can you make sure that at every place this PR touches `const` makes sense? I found out recently that we can be quite good at pretending that something is `const`, all the way down until we realize we need a `const_cast`, because modification is required in that one place.

I'm not quite sure I understand the question. This PR doesn't add any `const_cast`, and `const` is checked by the compiler so a successful build shows that we're never modifying something declared `const`. What additional work are you wanting?

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