[9.x] Implement Data::find() support for Runway models

[duncanmcclean]

This pull request implements Data::find() support for Runway models, allowing them to be resolved via their reference string (e.g. runway::post::uuid).

This was needed because Statamic 6's new ReplicatorSetController uses Data::find() to resolve the parent model when adding sets. Without this, users encountered a database error:

SQLSTATE[22P02]: invalid input syntax for type uuid: 'runway::{model}::{uuid}'

This PR implements it by:

1. Changing the DataRepository registration key from runway-resources to runway to match the reference prefix used by Runway models
2. Adding a find() method to ModelRepository that parses handle::id references and returns the corresponding Eloquent model

Fixes #809

[github-actions]

Released as part of v9.5.0.