have script function handle $total_test save/restore

$total_test is a global value to simplify the code but
when script is called recursively to create a new file
$total_test needs to start counting again and be restored back
to the correct value.
Change description for column related tests.

THe column releated tests that allow a schema require a description.
This was hard coded to 'pgtapgen'. This is useless in tests results
and makes finding the problem very difficult.

The description is now the schema.table.column_name with an suffix
to hint at which particular test it might be.