Have ValidateTopology check side-labels of edges

[strk]

At this time ValidateTopology is NOT checking that the edges forming a ring (based on next_right_edge, next_left_edge) have consistent face labeling on the side they are walked though.

Chances are such invalidities will be reported by edge coverage check, but the edge coverege check is pretty expensive and might be skipped if we checked for side-labeling validity instead.

[strk]

WIP: ​https://gitlab.com/postgis/postgis/-/merge_requests/42

[Sandro Santilli <strk@…>]

In 8b0ecf66/git:

Implement side labeling check in ValidateTopology

Closes #4944
Includes regress test catching new error (swapped side-labels)
Updates test expectances as we're now getting more errors.