fix(solc): process all imports even input files

[mattsse]

Motivation

This fixes a multi version build bug that caused foundry-rs/foundry#4320

the previous graph import resolve step did not take into account that a dependency can be used by multiple versions in the same project.

Solution

• process all dependencies of each file regardless if its a file of the project itself or an import.
• Keep track of handled dependencies for efficiency

With this fix sources are cloned (because they could be used by multiple versions), this is negligible but could be improved by wrapping the file content in an Arc.

PR Checklist

• Added Tests
• Added Documentation
• Updated the changelog
• Breaking changes