Add TextViewDelegate Option to Coordinators

[thecoolwinter]

Description

Main Changes:

• Adds the ability to conform TextViewCoordinators to TextViewDelegate (from CETV), forwarding most delegate messages to each conforming coordinator. This allows coordinators to receive detailed text change information quickly and with much more detailed information than is given in notifications.
• Fixes a bug where delegate messages were not sent when modifying text in filters.

Details:

• Raises ownership of coordinators to the TextViewController, which weakly references all coordinators. The controller now also handles forwarding messages, which was previously handled by the SwiftUI coordinator.
• The SwiftUI coordinator is simplified due to not having to manage the coordinator messages.
• Updated documentation for coordinators, explaining why the API exists and describes the new delegation API.

Related Issues

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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

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