[clang][deps] Ensure deterministic order of TU '-fmodule-file=' arguments

Translation units with multiple direct modular dependencies trigger a non-deterministic ordering in `clang-scan-deps`. This boils down to usage of `std::unordered_map`, which gets replaced by `std::map` in this patch.

Depends on D103526.

Reviewed By: dexonsmith

Differential Revision: https://reviews.llvm.org/D103807