fix: Improve accessibility of FieldAngle

[gonfunko]

The basics

• I validated my changes

The details

Proposed Changes

This PR updates FieldAngle to improve its accessibility and compatibility with Blockly v13. Specifically, it:

• Adds "angle" as the ARIA type of the field
• Customizes the ARIA description to "X degrees"
• Adjusts focus management such that the field editor has focus rather than the visual angle picker, to ensure that values can be typed in by default
• Announces the new angle value when interacting with the angle picker using the mouse or using the up and down arrow keys to step the value
• Fixes the alignment of the º symbol relative to the rest of the text on v13