Custom grid data API

[moonheart08]

MapGrid is inflexible and doesn't support user data (i.e. custom tile structures)

That is fine, what is not fine is our lack of ways to create new grid components to store other data (like atmospherics information, light levels, etc.)

I have a partial prototype for this I would like to dogfood and upstream, but it's currently blocked on engine changes.

Blocked on

• Allow static abstract through the sandbox + INumber #6432
• EntityQuery refactor. #6446