refactor: use AXUIElement extension

[ShlomoCode]

Describe your changes

Use AXUIElement extension methods (based of https://github.com/lwouis/alt-tab-macos/blob/master/src/api-wrappers/AXUIElement.swift) for shorter and more readable code

The AXUIElement extension it's just a thin wrapper over the macOS AX APIs, which saves the call success check and dealing with the inout variable and types, etc.

Related issue number(s) and link(s)

Checklist before requesting a review

• I have performed a self-review of my code
• If this change affects core functionality, I have added a description highlighting the changes
• I have followed conventional commit guidelines

Core Functionality Changes

There shouldn't be any functional change

[ShlomoCode]

I'm not handling DockObserver.swift here as I'm going to rewrite the whole thing into the more efficient way from PR #214.

[ejbills]

Good to merge?

[ShlomoCode]

@ejbills Yes it's ready to merge. Do you like the changes?

[ejbills]

@ejbills Yes it's ready to merge. Do you like the changes?

Yes! Reduces our repeated AXUIElement code blocks. Nice addition.