fix sqllogictest harness to use float rounding

[jycor]

When we generated the results for MySQL (specifically the float results), we used the golang fmt.Sprintf('%.3f') string, even for decimal types. Meanwhile, the doltharness was using decimal.Round(). There's evidently a difference in the way these two rounding operations work, so we had some failures due to rounding errors.

This PR makes it so decimals are rounded the same way floats are, so that results are consistent.

[coffeegoddd]

@jycor DOLT

comparing_percentages
99.998653 to 99.998602

version	result	total
4e38973	not ok	83
4e38973	ok	5937374

version	total_tests
4e38973	5937457

correctness_percentage
99.998602

[coffeegoddd]

@jycor DOLT

comparing_percentages
99.998653 to 99.998602

version	result	total
a1ee787	not ok	83
a1ee787	ok	5937374

version	total_tests
a1ee787	5937457

correctness_percentage
99.998602

[coffeegoddd]

@jycor DOLT

comparing_percentages
99.998653 to 99.998771

version	result	total
0e933ab	not ok	73
0e933ab	ok	5937384

version	total_tests
0e933ab	5937457

correctness_percentage
99.998771

[max-hoffman]

lgtm but a test for a query that fails without this would be nice

[coffeegoddd]

@jycor DOLT

comparing_percentages
99.998669 to 99.998787

version	result	total
4847a98	not ok	72
4847a98	ok	5937385

version	total_tests
4847a98	5937457

correctness_percentage
99.998787

[github-actions]

@coffeegoddd DOLT

test_name	detail	row_cnt	sorted	mysql_time	sql_mult	cli_mult
batching	LOAD DATA	10000	1	0.05	0.8
batching	batch sql	10000	1	0.07	1.43
batching	by line sql	10000	1	0.07	1.43
blob	1 blob	200000	1	0.89	3.09	3.51
blob	2 blobs	200000	1	0.9	3.9	4.46
blob	no blob	200000	1	0.88	1.32	1.42
col type	datetime	200000	1	0.81	1.75	1.93
col type	varchar	200000	1	0.68	1.81	1.88
config width	2 cols	200000	1	0.78	1.27	1.28
config width	32 cols	200000	1	1.85	1.38	2.58
config width	8 cols	200000	1	0.98	1.91	1.58
pk type	float	200000	1	0.87	1.22	1.23
pk type	int	200000	1	0.99	0.98	1.04
pk type	varchar	200000	1	1.5	1.12	0.95
row count	1.6mm	1600000	1	5.63	1.49	1.56
row count	400k	400000	1	1.38	1.46	1.51
row count	800k	800000	1	2.78	1.49	1.52
secondary index	four index	200000	1	3.48	1.11	0.95
secondary index	no secondary	200000	1	0.87	1.29	1.43
secondary index	one index	200000	1	1.11	1.5	1.48
secondary index	two index	200000	1	1.91	1.27	1.15
sorting	shuffled 1mm	1000000	0	4.81	1.9	1.89
sorting	sorted 1mm	1000000	1	4.79	1.91	1.9

[github-actions]

@coffeegoddd DOLT

name	detail	mean_mult
dolt_blame_basic	system table	1.06
dolt_blame_commit_filter	system table	2.71
dolt_commit_ancestors_commit_filter	system table	0.84
dolt_commits_commit_filter	system table	1
dolt_diff_log_join_from_commit	system table	1.64
dolt_diff_log_join_to_commit	system table	1.65
dolt_diff_table_from_commit_filter	system table	1.08
dolt_diff_table_to_commit_filter	system table	1.1
dolt_diffs_commit_filter	system table	0.97
dolt_history_commit_filter	system table	1.37
dolt_log_commit_filter	system table	0.94

[github-actions]

@coffeegoddd DOLT

name	add_cnt	delete_cnt	update_cnt	latency
adds_only	60000	0	0	0.73
adds_updates_deletes	60000	60000	60000	3.72
deletes_only	0	60000	0	1.89
updates_only	0	0	60000	2.38