[testlib] put postgres test database in test/data/database directory with other (sqlite) test databases. Closes #9240765 Simplify .hgignore in passing.

[dataimport] make eids_seq_range as massive store instance attribute again I changed it to a class attribute recently, but on further thought (and prompting from Adrien) it seems to make more sense as an instance attribute.

[dataimport] stop supporting None as eids_seq_range It couldn't work as-is because entities_id_seq is not a sequence object.