test that shows `getRowsUpdated` returns 0 in upsert

[sebastian-alfers]

Not really a fix, but a test that shows that getRowsUpdated does not return 1 for an inserted row in an upsert query.

An upsert is basically update ... if @@ROWCOUNT = 0 insert ...

[sebastian-alfers]

I tried to fix it, but did not really come to a point beside writing a reproducer as a test - which is why I created this draft pr instead of making an issue. Should I do the latter as well?