[estebanzimanyi]

MobilityDB declares jsonbsetExtractPath and jsonbsetExtractPathText with
null_handle text DEFAULT 'use_json_null', and jsonbsetInsert with after
boolean DEFAULT false. shape_text_array registers the path functions over
a set, and shape_sig_call, which registers the forms a default allows,
reads no set operand, so the set functions register their full form
alone.

shape_text_array registers, for a set operand, each form its trailing
defaults allow: text_array_default_forms states each shorter tail, the
omitted argument a literal sig_call_literal converts from its default,
and each form is its own body, Gen__v, beside the full one.

Witness: jsonbsetExtractPath(set([jsonb '{"a":{"b":7}}']), ['a','b'])
finds no function on main, where the extension lists the three-argument
form alone; it answers {7}, as MobilityDB does.

Measured: the generator run before and after the change on the catalog of
the pinned MEOS e87fd59846 registers 10103 and 10106 signatures: three
added, jsonbsetExtractPath and jsonbsetExtractPathText without their null
handling and jsonbsetInsert without its after, and none removed. The new
bodies call jsonbset_extract_path with
null_handle_type_from_string("use_json_null") and jsonbset_insert with
false.

Tests: value_type_sets.test runs each short form against its full form
with the default passed.

Why: a binding registers the SQL surface MobilityDB declares, and a call
leaving a defaulted argument out is part of it.