Add Definition support for routes

[andyw8]

This PR adds support for the Definition request for Rails routes. This allow jumping from names route, e.g. new_user_path, to the corresponding route declaration, e.g. in routes.rb.

The implementation is based on @tenderlove's prototype in https://github.com/tenderlove/refreshing, and uses the behaviour added by @luanzeba and others in https://github.com/rails/rails/pull/47877.

Notes:

• For Sorbet projects using the Tapioca DSL generators for routes, the Definition Lookup will return two results - one for the RBI file, and one for the actual route.

• ~For Shopify folk: Unfortunately this doesn't work on Core, the source location always point to a super call in routing_annotations.rb. bin/rails routes --expanded has the same problem.~ As of 2024-06-17 this is now working.

TODO:

• [x] confirm there is minimal performance impact for apps with a large number of routes
• [x] verify it doesn't break on older versions of Rails

Testing

It's working well on Identity, (which doesn't use Sorbet) and Code DB (which does use Sorbet).

[andyw8]

Still a few things to finalize but this is ready for a first round of feedback.

[andyw8]

For Shopify folk: This now works in Core