[Feature] Controller/general sub-asset tools

[DorCoMaNdO]

Akin to Dreadrith's Controller Editor:

• Sub-asset browsing
  • Currently selected objects should be highlighted
  • Allow selection via name labels
  • Split/organize by type
• Sub-asset hiding/unhiding
• Sub-asset removal (not cleanup, just direct removal of an object within the asset, present a warning for objects in use/always)
• Sub-asset exporting (prompt upon file name conflict)
  • This was a fairly hidden feature, added to the context menu of states' inspector icon, assets could only be exported if they were the motion of a state, and only that specific motion was exported, but multiple assets could be exported at once when multiple states were selected, however there was no conflict resolution, so when performed on multiple items with the same name (which can happen based on naming convention when exporting multiple child blendtrees of a large DBT), they would overwrite each other and create missing references as a result.
• Sub-asset embedding
  • This was accessed the same way as above

CE only supported these features for animator controllers but these could be generalized.

CE reference: