feat: split functionality into publishable crates

[alexfertel]

This PR enables using bulloak-syntax and bulloak-foundry as standalone crates, making it easier to plug different backends into the tree-parsing frontend of bulloak.

TODO:

• Move tree-splitting into bulloak-syntax.
• Flesh out public API.

[codecov]

Codecov Report

Attention: Patch coverage is 94.26230% with 21 lines in your changes missing coverage. Please review.

Project coverage is 93.3%. Comparing base (4d7be31) to head (6e99456).

Additional details and impacted files

Files	Coverage Δ
crates/bulloak/src/check.rs	91.4% <100.0%> (ø)
crates/bulloak/src/main.rs	100.0% <100.0%> (ø)
crates/bulloak/src/scaffold.rs	82.0% <100.0%> (ø)
crates/foundry/src/check/context.rs	86.3% <100.0%> (ø)
crates/foundry/src/check/location.rs	100.0% <100.0%> (ø)
crates/foundry/src/check/rules/structural_match.rs	96.8% <100.0%> (ø)
crates/foundry/src/check/utils.rs	93.3% <100.0%> (ø)
crates/foundry/src/config.rs	100.0% <100.0%> (ø)
crates/foundry/src/hir/hir.rs	75.0% <100.0%> (ø)
crates/foundry/src/hir/mod.rs	100.0% <100.0%> (ø)
... and 20 more