Correctly support foreign key constraint violation checks during merge

[zachmu]

This PR is mostly tests. See dolthub/dolt#10418 for most of the logic.

[github-actions]

	Main	PR
covering_index_scan_postgres	533.08/s	533.90/s	+0.1%
index_join_postgres	120.02/s	119.16/s	-0.8%
index_join_scan_postgres	177.61/s	177.94/s	+0.1%
index_scan_postgres	10.92/s	11.09/s	+1.5%
oltp_point_select	2188.23/s	2183.06/s	-0.3%
oltp_read_only	1625.64/s	1636.04/s	+0.6%
select_random_points	107.19/s	108.16/s	+0.9%
select_random_ranges	403.73/s	406.74/s	+0.7%
table_scan_postgres	10.78/s	10.92/s	+1.2%
types_table_scan_postgres	5.06/s	5.14/s	+1.5%

[github-actions]

	Main	PR
Total	42090	42090
Successful	17557	17557
Failures	24533	24533
Partial Successes1	5583	5583

	Main	PR
Successful	41.7130%	41.7130%
Failures	58.2870%	58.2870%

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. ↩

[Hydrocharged]

LGTM! Love the tests