State the array arguments a function reads

[estebanzimanyi]

The shape says which arrays a function ANSWERS and leaves the ones it READS to
each binding to recognise, and the only thing there to recognise them by is the
length parameter's name. Those names disagree across the surface — count,
count1, size, ngeoms, keys_len, path_len, pixels_size, wkb_size —
so a binding that knows some of them silently drops the rest, and
geo_cluster_kmeans, jsonb_delete_array and their kin reach no binding at
all.

shape.inputArrays states them, the sibling of arrayReturn and
outputArrays: the parameter, the parameter its length comes from, and the
element type with one pointer level off. 158 arguments across the surface.

The discriminator is the one this module already reads in the other direction.
An output array's length is passed BY POINTER, since the callee fills it in; an
input array's is passed BY VALUE, since the caller already knows it. So an
input array is a parameter that is an array of pointers or of by-value scalars
followed by a by-value integer — jsonb_each's written-back Jsonb **values
is not one, its int *count saying so.

A pointer to a MEOS VALUE type beside an integer is a value and a number, never
an array: text_left(text *txt, int n) takes one text and a character count,
jsonb_hash_extended one jsonb and a seed, interval_in one string and a
typmod. Only a pointer to a C scalar is an array of them, and char * is a
string in every binding rather than an array of characters.

Six tests hold the rule to those cases, the two that already stated an input
array is not an output one now stating what it is instead.