Re: pgbench - allow to create partitioned tables

Attached v9:

- remove the PART_UNKNOWN and use partitions = -1 to tell
that there is an error, and partitions >= 1 to print info
- use search_path to find at most one pgbench_accounts
It still uses left join because I still think that it is appropriate.
I added a lateral to avoid repeating the array_position call
to manage the search_path, and use explicit pg_catalog everywhere.
- let the wrongly repeated test name as is
- somehow use pg_checksums tablespace creation method, however:
- I kept testing that mkdir succeeds
- I kept escaping single quotes, if the path contains a "'"
so the only difference is that on some msys platform it may
avoid some unclear issue.

--
Fabien.