The DB connection should be provided in all cases as the first argument.
The overloaded function signatures will be removed in the future.
Warn about this change.
Part of https://wiki.php.net/rfc/deprecations_php_8_1.
Add some tests to cover related codepaths.
With the small caveat that the ones in build_assignment_string()
still don't seem to be tested as it looks the condtions are checked
beforehand, might need some more investigation.
Closes GH-6226
