Reject branch names that differ only by case

[elianddb]

Branch names are matched case-insensitively causing branches that only differ by case to resolve to the same data (e.g., main and Main).

• Refuse to create branch whose names differs from existing one by case on checkout, branch, and other variants

dolt branch Main
dolt checkout -b Main
dolt branch -c main Main
dolt branch -f Main

• Allow case-only rename to remove ambiguity of conflicting branch names
  Fix Dolt allows the creation of branches of the same name with different cases, but dolt checkout does not support this #11270

[coffeegoddd]

@elianddb DOLT

read_tests	from_latency	to_latency	percent_change
covering_index_scan	2.3	2.3	0.0
groupby_scan	142.39	142.39	0.0
index_join	1.93	1.93	0.0
index_join_scan	1.32	1.34	1.52
index_scan	219.36	219.36	0.0
oltp_point_select	0.25	0.25	0.0
oltp_read_only	5.0	5.0	0.0
select_random_points	0.51	0.51	0.0
select_random_ranges	0.64	0.65	1.56
table_scan	200.47	200.47	0.0
types_table_scan	467.3	467.3	0.0

write_tests	from_latency	to_latency	percent_change
oltp_delete_insert	6.21	6.21	0.0
oltp_insert	3.13	3.13	0.0
oltp_read_write	11.24	11.24	0.0
oltp_update_index	3.3	3.3	0.0
oltp_update_non_index	3.02	3.02	0.0
oltp_write_only	6.32	6.32	0.0
types_delete_insert	6.79	6.79	0.0

[coffeegoddd]

@elianddb DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
c0c6afd	ok	5937471

version	total_tests
c0c6afd	5937471

correctness_percentage
100.0

[coffeegoddd]

@elianddb DOLT

test_name	from_latency_p95	to_latency_p95	percent_change
tpcc-scale-factor-1	45.79	45.79	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	9e80d3a	52.65	dolt	cf30abf	52.63	-0.04

[coffeegoddd]

@elianddb DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
cf30abf	ok	5937471

version	total_tests
cf30abf	5937471

correctness_percentage
100.0