Remove deprecated loadState and saveState from addonHandler

[lukaszgo1]

Link to issue number:

Removes code deprecated as part of PR #12792

Summary of the issue:

PR #12792 converted state in addonHandler to a class deprecating some module level functions in the process.

Description of how this pull request fixes the issue:

Deprecated loadState and saveState are removed from addonHandler.

Testing strategy:

With git grep made sure that these functions are not used anywhere in the source code.

Known issues with pull request:

None known

Change log entries:

For Developers

• Functions loadState and saveState are removed from addonHandler - please use addonHandler.state.load and addonHandler.state.save instead.

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English

[seanbudd]

Thanks @lukaszgo1