Read from the catalog which arguments are arrays

[estebanzimanyi]

An array argument is one parameter to the caller and two to MEOS, the pointer
and its length, and the layer told them apart by the length's NAME. The surface
spells that length eight ways — count, count1, count2, size, ngeoms,
keys_len, path_len, pixels_size — so the rule reached the two it knew and
left the rest, and it had to exclude the receiver by hand because set_value_n
looks the same as an array beside its length.

shape.inputArrays names each array, the parameter its length comes from and
its element type, so the layer reads it and both problems go: a length is found
whatever it is called, and a receiver is no array because the catalog does not
say it is one. 14 methods more — Jsonb.ExistsArray, Jsonb.DeleteArray,
Geo.ClusterKmeans, Geo.ClusterWithin and their kin, whose lengths are
keys_len and ngeoms — 1246 methods against 1232, 49 deferred against 63.

Two tests take an array each: a geometry set built from an array of geometries,
and a jsonb asked which of an array of keys it holds, whose length MEOS calls
keys_len.