Rank Suggestions by Self-Type Specificity

[iamrecursion]

Pull Request Description

This PR ensures that self-type suggestions are ranked by type specificity. This means that Any methods will show up last instead of first. If, for example, a search is done on Integer, it will show methods on Integer, then methods on Number, then methods on Any.

Closes #1627.

Important Notes

This is not the most efficient implementation as I can't work out how to use the slick DSL to encode the same logic inside the database query. That is a possible enhancement for the future.

Checklist

Please include the following checklist in your PR:

• The documentation has been updated if necessary.
• All code conforms to the Scala, Java, and Rust style guides.
• All documentation and configuration conforms to the markdown and YAML style guides.
• All code has been tested where possible.

[4e6]

LGTM