contrib/cube has a limit to 100 dimensions for cube datatype.  However, it's
not enforced everywhere, and one can actually construct cube with more than
100 dimensions having then trouble with dump/restore.  This commit add checks
for dimensions limit in all functions responsible for cube construction.
Backpatch to all supported versions.

Reported-by: Andrew Gierth
Discussion: https://postgr.es/m/87va7uybt4.fsf%40news-spur.riddles.org.uk
Author: Andrey Borodin with small additions by me
Review: Tom Lane
Backpatch-through: 9.3