[ty] fallback to resolve_real_module in file_to_module (#20461)
This is a naive(?) implementation of the approach @MichaReiser
originally suggested to me in https://github.com/astral-sh/ty/issues/869
Fixes https://github.com/astral-sh/ty/issues/869
Fixes https://github.com/astral-sh/ty/issues/1195
