Replace AutoFill with better property-picking UI

[j9liu]

Description

In UCesiumFeaturesMetadataComponent, the "AutoFill" function is a quick way to grab all of the metadata and feature ID sets on visible tiles, but it does not provide an easy editing experience. The nested storage of properties makes navigating the component's UI very cumbersome, and it gets worse for datasets with huge amounts of varying properties (think Cesium OSM Buildings).

This PR replaces "Auto Fill" with a new window that allows for incremental addition of feature ID sets / properties to the tileset.

There is room for UI improvements that probably won't be in scope for this PR:

• Search bar
• Sorting
• Multi-selection

Issue number or link

No direct issue, but this is to support some of the UI concerns in #1685.

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.

Testing plan

TODO

• San Francisco Ferry Building
• Cesium OSM Buildings
• Muscatatuk (property textures)
• Feature ID texture with KHR_texture_transform
• Property texture property with KHR_texture_transform
• glTF with offset / scale / noData / default properties