Make query resolver more generic

[koesie10]

This will make the query resolving functionality currently used for contextual queries more generic and usable for resolving other types of queries as well (e.g. based on tags instead of on id). This is in preparation for #2633. There should be no changes in behavior, except for a single changed error message (which adds kind "definitions", to the error message, so shouldn't really have any influence).

It's easiest to review this commit-by-commit.

Checklist

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.

[robertbrignull]

LGTM

As far as I can tell this is just extracting functions to new files without changing them significantly. And I appreciate that you added more tests.