Update dolt_verify_constraints() stored procedure to support all constraint types

[fulghum]

Removing the wording that says only FK constraints are supported.

Also updated the result description – the docs stated we returned a count of the violations, but the code was actually just returning 0 for no violations and 1 for violations. This would be nice to fix so that we return the actual violation count, but I think we should look at migrating dolt constraints verify to the stored procedure first, since it will likely require other result changes, and then we can batch them together in one minor version update.

Related to: dolthub/dolt#7679

[timsehn]

What does this mean?

DOLT_VERIFY_CONSTRAINTS by default does not detect constraints for row changes

[fulghum]

What does this mean?

DOLT_VERIFY_CONSTRAINTS by default does not detect constraints for row changes

The rest of that sentence, on the next line (hidden by the diff on GitHub), is "that have been previously committed." – so it's just saying, that by default, dolt_verify_constraints() only detected changes in the working set, but you can use the --all flag to verify all data, even rows that have already been committed.

[timsehn]

Cool LGTM.