Refactor code into new JsonbValueAsText, and use it more
jsonb_object_field_text and jsonb_array_element_text both contained
identical copies of this code, so extract that into new routine
JsonbValueAsText. This can also be used in other places, to measurable
performance benefit: the jsonb_each() and jsonb_array_elements()
functions can use it for outputting text forms instead of their less
efficient current implementation (because we no longer need to build
intermediate a jsonb representation of each value).
Author: Nikita Glukhov
Discussion: https://postgr.es/m/
7c417f90-f95f-247e-ba63-
d95e39c0ad14@postgrespro.ru