feat(solc): handle conflicting artifacts properly

[mattsse]

Motivation

Closes #1487

this changes how output files are computed and now takes possible conflicts into account.

this doesn't change how artifacts were emitted up to now and only adds extra logic if there are conflicting files.

maybe there'll be some edge cases with caching, but hard to anticipate at this point.

this also passes all existing foundry tests with a patched version

Solution

change emit logic:

1. compute all output files as before but keep track of conflicting contracts
2. adjust conflicting paths by finding a unique alternative path, traversing the sol file and prepending the parent dir(s) to the output file. this will always find a unique output path

PR Checklist

• Added Tests
• Added Documentation
• Updated the changelog