Go tests for the COPY command

[zachmu]

These are all lifted from the bats tests. I'm gearing up to make major changes to how COPY works to support more customer schemas and want to these tests to help.

[github-actions]

	Main	PR
covering_index_scan_postgres	362.78/s	363.67/s	+0.2%
index_join_postgres	153.69/s	154.40/s	+0.4%
index_join_scan_postgres	183.89/s	185.19/s	+0.7%
index_scan_postgres	12.64/s	12.64/s	0.0%
oltp_point_select	2809.95/s	2779.50/s	-1.1%
oltp_read_only	1850.14/s	1859.38/s	+0.4%
select_random_points	112.52/s	111.45/s	-1.0%
select_random_ranges	129.60/s	130.86/s	+0.9%
table_scan_postgres	12.06/s	12.03/s	-0.3%
types_table_scan_postgres	5.66/s	5.70/s	+0.7%

[github-actions]

	Main	PR
Total	42090	42090
Successful	15350	15350
Failures	26740	26740
Partial Successes1	5233	5233

	Main	PR
Successful	36.4695%	36.4695%
Failures	63.5305%	63.5305%

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! 🙌