Add CesiumAzureMapsRasterOverlay

[j9liu]

Description

Depends on CesiumGS/cesium-native#1264.

This PR adds support for streaming Azure Maps with a subscription key. It also:

• Fixes Small credits bug with Google 2D Maps overlays #1742.
• Exposes the Refresh button on overlays in the editor.

Base + Relative Traffic overlaid:

Imagery + Infrared Weather overlaid:

Author checklist

• I have done a full self-review of my code.
• I have updated CHANGES.md with a short summary of my change (for user-facing changes).
• [ ] I have added or updated unit tests to ensure consistent code coverage as necessary.
• I have updated the documentation as necessary.

Remaining Tasks

• Streaming from Cesium ion still needs to be tested, but the backend to enable that is still WIP.

Testing plan

Pretty straightforward; play around with the different tileset ID options on the overlay.

[kring]

Thanks @j9liu!