Fix tileSize for non-geospatial use-case

[ilan-gold]

For #5811 - this PR solves the problem by basically reverting #4616 for the non-geospatial use-case. As I mentioned, though, the only problem now is that I have come to rely on the ability to change the zoom level at which tiles are fetched in the non-geospatial case.

Should I follow this PR up with another that allows the user to offset the zoom level in the non-geospatial instance? Should this PR not revert the changes from #4616 and just document what people need to do with regards to the tileSize prop when they are using the TileLayer in the non-geospatial use-case.

Change List

• Revert TileLayer: adjust zoom by tileSize #4616 in the non-geospatial use-case

[coveralls]

Coverage increased (+0.005%) to 82.354% when pulling 0329f45 on ilan-gold:infovis_tile_offset into 732a1c0 on visgl:master.

[Pessimistress]

Can you review the indexing system and tileSize sections of the documentation and see if this change can be explained in a way that is clear and (ideally) inconsistent with the geospatial use case? Can we just reference the DZI spec for non-geospatial the same way we use OSM?

Where tileSize does not intuitively define the desired "zoom offset", can we expose something else for the user to customize the layer behavior?

[ilan-gold]

@Pessimistress Sounds like a plan. I'll add the documentation for this PR and open another for the new prop then to control the "zoom offset."

[ilan-gold]

Closing in favor of #5895