Prevent Chromium Enhanced UI performance regression

[culpen90]

Summary

• add automatic Enhanced UI handling for recognized Chromium browsers
• disable Enhanced UI when a recognized browser starts or activates, and leave it disabled after Rectangle window adjustments
• preserve restore behavior for other apps, VoiceOver, Switch Control, and existing explicit modes
• document the available modes and add regression coverage for the policy and preference migration

Fixes #1751

Testing

• EnhancedUITests: 8 passed
• Full Rectangle test suite: 242 passed

[rxhanson]

Thanks for tackling this one, too! I'm typically not thrilled about having to maintain a list of bundle identifiers, but I'm thinking that this might be the way this one has to go. Will test it out soon.