mesh_plot for xx should be quadmesh for xx ...

[mdsumner]

This should provide opportunities for the next level refactor.

• [ ] simplify mesh_plot dispatch by putting logic in mesh_plot.quadmesh
• [ ] put as much format handling into quadmesh() rather than the plot
• [ ] consider a rasterish() to get extent, dimension, crs, coords as necessary from raster, terra, stars, spatstat, etc
• [ ] could even deal with non-materialized forms by using vapour, or terra ? I think dep on terra is worthwhile atm
• [ ] review stuff in this tweet https://twitter.com/Reichstein_BGC/status/1456381118232633352?t=r15bwr1t4-pPNWQWNuAROA&s=19