Re-write the module override logic.

This makes the product-installed-files macro more accurately reflect
the files installed for a given product, as well as fixing bugs in
the previous implementation.

Specifically, the complete list of overrides found so far is stripped
in each round of expanding required modules. Previously, overrides were
stripped out *after* expanding required modules. This meant that for a
scenario where B depends on C, and A overrides B, C could get installed.
It's unclear if this was a problem in practice.

The other effect is that the offending artifacts txt is more accurate,
since overridden modules are now correctly removed.

Bug: 80410283
Test: build_test downstream
Change-Id: I8bfc7c40bedd5cb2afba567bae4b998f51770793