pg_type index implementation

[NathanGabrielson]

Adds the two internal indices that should exist on pg_type. Very similar to the existing implementation of pg_class.

[github-actions]

	Main	PR
covering_index_scan_postgres	1077.40/s	1095.91/s	+1.7%
index_join_postgres	158.11/s	157.32/s	-0.5%
index_join_scan_postgres	205.64/s	203.68/s	-1.0%
index_scan_postgres	12.11/s	12.06/s	-0.5%
oltp_point_select	2393.98/s	2378.71/s	-0.7%
oltp_read_only	1842.37/s	1825.39/s	-1.0%
select_random_points	129.41/s	127.12/s	-1.8%
select_random_ranges	825.38/s	827.53/s	+0.2%
table_scan_postgres	11.81/s	11.76/s	-0.5%
types_table_scan_postgres	5.45/s	5.43/s	-0.4%

[github-actions]

	Main	PR
Total	42090	42090
Successful	17891	17891
Failures	24199	24199
Partial Successes1	5626	5626

	Main	PR
Successful	42.5065%	42.5065%
Failures	57.4935%	57.4935%

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. ↩

[fulghum]

Looks good! Just a couple very minor suggestions.

[fulghum]

(minor) You may want to add an EXPLAIN SELECT test here, too. Otherwise we aren't testing that this is actually using the index during the join, which I think is what you want to test here.

[fulghum]

(minor) Looks like these are only used in the pgcatalog package, so you could lower case them to avoid exporting them to all packages. Not a huge deal, but always nice to keep things package private if possible and avoid those symbols being available in other packages if they aren't needed yet.