Reduce Text Artifacts, Fix Layout Bug, Public Undo Manager

[thecoolwinter]

Description

• Reduces text drawing artifacts by turning off font smoothing, enabling subpixel positioning and font quantization, and a hidden smoothing API.
• Adds an internal ObjC target to accomplish the previous point.
• Fixes a layout bug where layout bounds would be nearly infinite due to the view being told to lay out but not be in the view hierarchy yet, causing a hang and memory explosion as every line in a potentially large document is laid out and rendered.
• Fixes a small bug with the undo manager's grouping behavior and makes it public (for a fix in CESE for undo-redo related bugs), as well as reordering some notifications in the undo manager.

Related Issues

• N/A

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

Before:

After (left CE, right Xcode):