Editor: Mesh instance reuse for objects in FBX importer

## Is your feature request related to a problem? Please describe.
FBX format supports a mesh structure reuse in it's objects

## Describe the solution you'd like
Need to track mesh instances during import and reuse meshes if it possible.
This will remove duplicates of meshes and will allow to use GPU instancing.

## Describe alternatives you've considered
n/a

## Additional context
n/a
