Speed up edge coverage checking in ValidateTopology

[strk]

The invalidities we're aiming to catch are those of holes advertised to be in a different face than the one really containing them.

The current code runs an ST_Contains() against all faces in each edge's bounding box and faces intersecting it. This is very expensive.

Instead, as the EdgeRings check is already building all rings, we could

1. Skip invalid rings
2. For remaining *hole* rings (CW rings) find the shell (CCW ring) with smallest area containing them
3. Compare the containing shell face id with the advertised one

[strk]

WIP: ​https://gitlab.com/postgis/postgis/-/merge_requests/44

[strk]

I'm satisfied for now, as of commit [30aeed6904b3b74eb26c5c4cf01e0e9c53a2b3fb/git] with the speed of validating edge containment

[Sandro Santilli <strk@…>]

In 63b1ea1a/git:

Further improve hole coverage speed by only comparing an hole point

References #4946