Add support for pg_get_serial_sequence(text,text)

[fulghum]

Adds support for the pg_get_serial_sequence(text,text) function, which returns the sequence owned by a column.

Example usage:

create table t1 (id SERIAL PRIMARY KEY);
SELECT pg_get_serial_sequence('t1', 'id');

[github-actions]

	Main	PR
Total	42090	42090
Successful	14426	14426
Failures	27664	27664
Partial Successes1	4690	4690

	Main	PR
Successful	34.2742%	34.2742%
Failures	65.7258%	65.7258%

Footnotes

1. These are tests that we're marking as Successful, however they do not match the expected output in some way. This is due to small differences, such as different wording on the error messages, or the column names being incorrect while the data itself is correct. ↩