Avoid name collisions for generated FK names

[fulghum]

Matches Postgres' behavior where default foreign key name collisions are resolved by adding an integer suffix to the name to make it unique.

Also includes a bug fix for setting the target schema when dropping a primary key.

Fixes a couple more issues with supporting DoltHub's schema in Doltgres.

[github-actions]

	Main	PR
covering_index_scan_postgres	401.03/s	397.23/s	-1.0%
index_join_postgres	155.14/s	154.71/s	-0.3%
index_join_scan_postgres	188.16/s	186.88/s	-0.7%
index_scan_postgres	12.36/s	12.60/s	+1.9%
oltp_point_select	2830.00/s	2804.08/s	-1.0%
oltp_read_only	1887.05/s	1880.27/s	-0.4%
select_random_points	112.15/s	112.12/s	-0.1%
select_random_ranges	135.32/s	135.19/s	-0.1%
table_scan_postgres	10.33/s	10.37/s	+0.3%
types_table_scan_postgres	5.43/s	5.42/s	-0.2%

[github-actions]

	Main	PR
Total	42090	42090
Successful	15710	15713
Failures	26380	26377
Partial Successes1	5194	5194

	Main	PR
Successful	37.3248%	37.3319%
Failures	62.6752%	62.6681%

${\color{lightgreen}Progressions (2)}$

alter_table

QUERY: alter table atacc1 alter column test drop not null;

QUERY: insert into atacc1 values (null);

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. ↩

[zachmu]

LGTM!