MVTAnnotationsPlugin: Add support for road labels

[gkjohnson]

Related to #1600
Related to #1647

Next

• Fix zoom out character squishing
• Test text / icon draw through / shift above terrain
• Add a "driver" class for encapsulating necessary annotation logic (points object, text object, font spacing, name retrieval etc)
• Add "snap" to new road, stick around if road is still present (even if no associated anchor) and it's visible for consistency.
• Prevent road annotation clash, Improve spacing between text strings - ensure they re not too close
• Fix points not being "corrected" based on highest LoD content / id

Follow Up

• Performance
• Mobile testing
• Polish
• Allow for regenerating all annotations on filter change, etc