Information about supported extensions in `ReflectAsset`

## What problem does this solve or what need does it fill?

I have type X, that type reflects Asset. I have registered loader for that type with extension ".super.json". I want to be able to get vec or slice of supported extensions for a given type from `ReflectAsset`.

## What solution would you like?

Add methods for accessing asset loader/saver/processor information to `ReflectAsset`.

Start by locating ReflectAsset and the existing asset loader, saver, and processor APIs. Trace how a reflected asset type reaches its registered extension information, then define completion as methods on ReflectAsset that expose the supported extensions and related loader, saver, or processor information for a given type.

Written by the indexing model from the issue text.