* Addressed feedback from previous PR
* Change missing entity aliases to be deterministic.
When converting slices, this helps produce the same results on multiple reconversions of the same data.
* Exposed the asset filter callback.
This allows the slice converter to specifically load nested slices as opposed to not loading *any* referenced assets.
* Added support for multiply-nested slice instance conversion.
(cherry picked from commit 86136ddfa6)
- Uses ToolsApplication instead of ComponentApplication so that built-in Editor components are recognized and read in correctly
- Starts up all the DynamicModules immediately so that the System Components are activated, which registers asset handlers and allows asset references to serialize in correctly
- Adds a -specialization command-line flag to specify which project specialization to use (editor, game, etc)
- Removes the filter to ignore unknown classes since they should all now be "known"
- Adds a few gem autoload flags and a null thumbnail service so that Qt and Python systems can be skipped, as they aren't needed for the data conversions and would bring additional overhead and complications