BUG: replace iterrows with itertuples in sql insert (GH6509)
Fixes #6509.

Should still add a test

@jreback I added a `check_exact` keyword. Is this what you had in mind?
 @jorisvandenbossche perfect.

assert_numpy_array_equal should prob be a module level function too (it just calls np.array_equal in any event), but no biggie.

in theory all functions should actually be on the TestCase, but too much work to fix

pls add a release note then merge 
 Should there be a release note? As this fixes something (the new sqlalchemy based sql functions) that is not yet released?
 oh right.....though like to reference the closed issue (maybe just add it to an existing one)
 Actually, it was also fixed in the legacy code. Anyway, added a line to release notes.
