Add preview and thumbnails to in-editor asset browser

[AMZN-Liv]

Is your feature request related to a problem? Please describe.
When I'm looking through my list of assets in the in-editor asset browser, I cannot easily figure out which file I need unless I remember the file name.

Describe the solution you'd like
Adding thumbnails to the core editor's asset browser for visual asset types (such as textures/images, materials, animations, slices, 3D models, particles, etc) would make it easier to find specific assets, which will reduce the amount of time it takes to search and place content. This feature will also need to account for a representation of non-visual asset files.