Update DoltTable.ProjectedTags() to distinguish between no set projectedCols and zero projectedCols

[angelamayxie]

fixes #10451

When getting ProjectedTags(), we were not distinguishing between when projectedCols was nil (meaning no projections are set so we should return all columns) and when projectedCols was an empty array of length 0 (meaning the table has been pruned to be zero columns but we still care about the number of rows), since in both cases, projectedCols would have a length of 0. This was causing LEFT OUTER JOINs that didn't project any left-side columns to not return the correct number of columns. This was fixed by checking for if projectedCols was nil instead (which is what we do in other functions like Projections() and HistoryTable.ProjectedTags()

Also some minor refactorings:

• renamed getIta to getIndexedTableAccess
• removed unused variables returned by getSourceKv

Test added in dolthub/go-mysql-server#3424

[coffeegoddd]

@angelamayxie DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
eaeb2f9	ok	5937471

version	total_tests
eaeb2f9	5937471

correctness_percentage
100.0

[coffeegoddd]

@angelamayxie DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
a14c812	ok	5937471

version	total_tests
a14c812	5937471

correctness_percentage
100.0

[coffeegoddd]

@coffeegoddd DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
dfb7daf	ok	5937471

version	total_tests
dfb7daf	5937471

correctness_percentage
100.0

[coffeegoddd]

@angelamayxie DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
1a28801	ok	5937471

version	total_tests
1a28801	5937471

correctness_percentage
100.0

[coffeegoddd]

@angelamayxie DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
677d1f8	ok	5937471

version	total_tests
677d1f8	5937471

correctness_percentage
100.0

[jycor]

LGTM

[jycor]

#benchmark-mini

[github-actions]

@jycor workflow run: https://github.com/dolthub/dolt/actions/runs/21847059663

[github-actions]

@jycor workflow run: https://github.com/dolthub/dolt/actions/runs/21847059663

[coffeegoddd]

@jycor DOLT

read_tests	from_latency	to_latency	percent_change
covering_index_scan	0.55	0.54	-1.82
groupby_scan	10.27	10.09	-1.75
index_join	1.86	1.82	-2.15
index_join_scan	1.34	1.34	0.0
index_scan	22.28	22.28	0.0
oltp_point_select	0.27	0.27	0.0
oltp_read_only	5.28	5.28	0.0
select_random_points	0.54	0.54	0.0
select_random_ranges	0.55	0.55	0.0
table_scan	22.28	22.28	0.0
types_table_scan	66.84	68.05	1.81

write_tests	from_latency	to_latency	percent_change
oltp_delete_insert	6.32	6.32	0.0
oltp_insert	3.07	3.07	0.0
oltp_read_write	11.45	11.45	0.0
oltp_update_index	3.19	3.19	0.0
oltp_update_non_index	3.13	3.13	0.0
oltp_write_only	6.09	6.09	0.0
types_delete_insert	6.91	6.79	-1.74

[coffeegoddd]

@jycor DOLT

test_name	from_latency_p95	to_latency_p95	percent_change
tpcc-scale-factor-1	61.08	61.08	0.0

test_name	from_server_name	from_server_version	from_tps	to_server_name	to_server_version	to_tps	percent_change
tpcc-scale-factor-1	dolt	f729910	37.8	dolt	677d1f8	37.58	-0.58

[coffeegoddd]

@angelamayxie DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
3366191	ok	5937471

version	total_tests
3366191	5937471

correctness_percentage
100.0