fix dolt push hanging on ssh askpass credential prompts

[elianddb]

dolt push over git+ssh could hang forever when ssh routed a credential prompt to an SSH_ASKPASS program.

• Remove askpass and prompt related environment keys from git subprocess environment.
  Fix dolt push to git+ssh GitHub remote hangs on Linux/WSL2 #11027

[coffeegoddd]

@elianddb DOLT

read_tests	from_latency	to_latency	percent_change
covering_index_scan	2.3	2.3	0.0
groupby_scan	139.85	139.85	0.0
index_join	2.0	2.0	0.0
index_join_scan	1.34	1.37	2.24
index_scan	215.44	215.44	0.0
oltp_point_select	0.24	0.24	0.0
oltp_read_only	4.91	4.91	0.0
select_random_points	0.55	0.55	0.0
select_random_ranges	0.65	0.65	0.0
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
b78243c	ok	5937471

version	total_tests
b78243c	5937471

correctness_percentage
100.0

[coffeegoddd]

@elianddb DOLT

test_name	from_latency_p95	to_latency_p95	percent_change
tpcc-scale-factor-1	45.79	44.98	-1.77

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	2a5de68	52.63	dolt	f950f81	52.95	0.61

[coffeegoddd]

@elianddb DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
f950f81	ok	5937471

version	total_tests
f950f81	5937471

correctness_percentage
100.0

[macneale4]

This seems like the wrong fix. It just disables the ability to use SSH_ASKPASS and the others. I don't think that's what the user wants - I would suspect they want to be prompted.

If a user has set that environment variables, they don't want us to silently ignore them. That's counter intuitive, and possibly harmful. We either need to print a loud message that we don't support these things and exit with a failure, or they need to work as expected.