Add the ability to read back (and edit) mvt

[autra]

Description

Provide a way to read back mvt tile content.

Context and use case

I'm using a table to cache feature simplification for visualization purpose (with pg_tileserv). The dataset is quite big (will be around 600GB).

I want to cache some x,y,z tile alongside the tile in mvt format. But after updating part of the underlying dataset, if I want to refresh the cache, I would need to update part of a mvt tile (or regenerate the whole pyramid, but that's not feasible in my case).

The solution I've chosen now is to to keep each mvtgeometry and aggregate only when visualizing, but I'd like to be able to do the extra mile and keep only the mvt. If it were possible, it would allow me to get better serving speed (and simplify the serving function).

Proposition

Implement a ST_FromMvt or ST_ExplodeMvt, or ST_DumpMvt that would basically do the reverse operation of ST_AsMvt.

Thanks!

(NB: to give the full story : the features are points that are currently stored with pgpointcloud extension.

[pramsey]

Milestone renamed

[robe]

In prep for 3.1.3 release