Improve library/import resolution

[mattsse]

Is your feature request related to a problem? Please describe.
Currently, resolving libraries is very primitive and basically only supports lookups in the configured lib folder without applying remappings.

Essentially all imports outside of the src directory rely on remappings so solc can apply them.
This means, they're not part of the cache since we don't discover them properly. Therefor changes in lib contracts can be skipped if caching is enabled

Likely the case here foundry-rs/foundry#299
also definitely related #727

Describe the solution you'd like
Short term:

• resolve remappings in resolve_libraries.
• check all imports contracts for changes when checking a CacheEntry

Long term, add a proper dependency graph implementation.