Implementing new methods from servercfg.DoltgresConfig

[fulghum]

Implements the new IsUserSpecified() and SkipRootUserInitialization() methods from servercfg.DoltgresConfig, added in dolthub/dolt#8690

[github-actions]

	Main	PR
covering_index_scan_postgres	370.21/s	369.48/s	-0.2%
index_join_postgres	153.03/s	152.53/s	-0.4%
index_join_scan_postgres	183.97/s	182.27/s	-1.0%
index_scan_postgres	12.54/s	12.35/s	-1.6%
oltp_point_select	2781.54/s	2773.47/s	-0.3%
oltp_read_only	1877.95/s	1867.68/s	-0.6%
select_random_points	112.21/s	111.66/s	-0.5%
select_random_ranges	131.12/s	133.95/s	+2.1%
table_scan_postgres	11.72/s	11.87/s	+1.2%
types_table_scan_postgres	5.42/s	5.60/s	+3.3%

[github-actions]

	Main	PR
Total	42090	42090
Successful	15383	15383
Failures	26707	26707
Partial Successes1	5237	5237

	Main	PR
Successful	36.5479%	36.5479%
Failures	63.4521%	63.4521%

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. ↩