Refresh StatusLEDs when theme changes

[vkbo]

Summary:

This PR adds the possibility to refresh the StatusLED widget colours when the theme changes,a nd switches to use the trinary enum for values instead of internal integer flags.

Related Issue(s):

Closes #1893

Reviewer's Checklist:

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All flake8 checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed