Revert "Actually disable the module generation tests." (#84527)

This reverts commit 0bbada93.

The update of Clang in the CI broke due to the new LLVM version naming.
It needs to look for the clang 18.1 package instead of 18. Since it
couldn't find 18 it used 17 as fallback. This gives ODR violations which
caused the output for the module test to be wrong. (It didn't crash
which would be a lot more obvious to debug.)

The clang-tidy selection was fixed by
https://github.com/llvm/llvm-project/pull/81362. That patch also makes
clang-19 work with clang-tidy-19 out of the box.

The time-out have not been addressed; that is a CI issue and not an
issue with this test. They run in 200-ish s so they are slow but far
below the 1500s threshold. (Due to a dependency in this test it can't be
split in multiple tests.)