Find and Replace Refactor

[thecoolwinter]

Description

@austincondiff has been building out the 'replace' functionality and realized the way we had structured the panel, controller, target, and model was extremely overcomplicating things. This PR is an attempt to fix that

Changes:

• Moves all 'business logic' into the FindPanelViewModel observable object. This includes clarified methods like find, replace, and moveToNextMatch/moveToPreviousMatch. All state has been moved to this object as well, out of a combination of both the SwiftUI view and the find view controller.
• Removes the FindPanelDelegate type entirely. All that type was doing was passing method calls from the find panel to it's controller. Since all that logic is now in the shared view model, the controller & view can just call the necessary methods on the model.
• Simplifies the FindViewController to only handle view/model setup and layout.
• Changes the focus state variable to an enum instead of two Bools. This fixes an issue where there was a moment of nothing being focused when switching between the find and replace text fields.
• Removes the unnecessary NSHostingView -> NSView -> SwiftUI View structure, replacing it with an NSHostingView subclass FindPanelHostingView that hosts a FindPanelView.
• Clarifies some view naming to reflect what each type does.
  • FindPanel -> FindPanelHostingView
  • FindPanelView search fields moved to:
    • FindSearchField
    • ReplaceSearchField

Related Issues

• feat: Find in Editor #295

Checklist

• I read and understood the contributing guide as well as the code of conduct
• The issues this PR addresses are related to each other
• My changes generate no new warnings
• My code builds and runs on my machine
• My changes are all related to the related issue above
• I documented my code

Screenshots

[thecoolwinter]

That was odd but opening/closing it made the merge work so there's no conflicts now. @austincondiff when you have time to take a look I'd appreciate feedback on these changes. It's a lot but I'm pretty certain I maintained all existing functionality, including the changes already on the branch for case sensitivity.

[austincondiff]

Nice work!