feat: support flutter_map v8

[JaffaKetchup]

This is still a work in progress.

• double tileSize -> int tileDimension is the biggest change throughout; I'm not 100% sure where the boundary is to stop renaming and changing the type - I guess the stylesheet must keep "tileSize"?
• The vector tile layer does not yet support unbounded horizontal scrolling

At some point, some coordination is planned to create a more versatile flutter_map tile layer, which can be more easily extended for a raster layer within FM, and other vector layers. This will mean a reduction of copied code, benefit from updates to the tile layer handler, and mean unbounded horizontal scrolling will be free. Other existing plugins can also take advantage of this.

[kekland]

I guess the stylesheet must keep "tileSize"?

Should be ok to rename it to tileDimension everywhere (including in shaders), if it'll benefit the consistency. The spec doesn't have a notion of "tileSize", it's up to the implementation.

and mean unbounded horizontal scrolling will be free

How does flutter_map handle this? Does it:

a) Draw each tile multiple times - e.g. draw each tile separately for each visible repetition of the world

b) Draw the entire world again - meaning, we render the world once, and then re-use the same world texture for the repetitions

First one would result in some performance penalties with the current implementation, since it'll require additional draw calls. However, the second one should be OK in terms of performance, since we can take the ui.Image that was created as a part of the "main world rendering", and then re-use that image to paint the visible world repetitions