Add a Color Input

[kaycodes13]

Summary of Changes

• Added ColorInput, an extension of TextInput specialized for handling Color input. It parses hex color codes in three formats (3-character RGB, 6-character RGB, and 8-character RGBA), has custom input validation, and has a preview swatch of the chosen colour beside the input field.
• Added a new generator method in ConfigEntryFactory so that ColorInputs can be automatically generated for ConfigEntry<Color>s.

Checklist

• No change is too small for a release, so pick one:
  • I have updated the package version following semantic versioning
  • There is another change actively WIP that will update the version (link issue or PR here)
  • This PR does not update user-facing code/config
  • I'm not sure how to set the version and would like the reviewer's help

[flibber-hk]

@kaycodes13 apologies for the large pile of commits... I have un-bumped the version because there are three other open PRs, if we clear the PRs and don't update the version please ping in #silksong-org-discussion.

If you do want to make further edits to this PR please pull first :zote:

[flibber-hk]

@dplochcoder I have rearranged the mod menu test area so that the nested testing plugin and the newly added auto testing plugin have been added to the main testing plugin's menu (rather than getting their own menu) - I think 3+ menus are a bit too much clutter for my taste. If you (or anyone else) want to browse the diff of that change in isolation then it's covered by this

[flibber-hk]

zote

[flibber-hk]

Hopefully the other PRs will be handled soon; I'd prefer to avoid multiple consecutive releases but if you want this on thunderstore asap feel free to poke and we can bump version