WIP rewrite for Craft 4

[ostark]

Discussions #68 & #65
Issue #67

So far no significant code changes, just structural.

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• Prepare for tests with pest
• Use Handler classes instead of closures
• Use DI Container instead of Service Locator (not everywhere so far)
• Move event listener setup to the main Plugin class (remove EventRegistrar)
• Refactor drivers (using https://github.com/Sammyjo20/Saloon)

[mattbloomfield]

Hey @ostark any progress here?