All partitioning functions now has the signature `int func(anyelement)`.
This cleans up some special handling that was necessary to support
the legacy partitioning function that expected text input.
This commit moves a lot of test setup logic to runner.sh. Also
passes the right commands to the regression infrastructure to create
appropriate users and run tests as a regular user.
Clean up the table schema to get rid of legacy tables and functionality
that makes it more difficult to provide an upgrade path.
Notable changes:
* Get rid of legacy tables and code
* Simplify directory structure for SQL code
* Simplify table hierarchy: remove root table and make chunk tables
* inherit directly from main table
* Change chunk table suffix from _data to _chunk
* Simplify schema usage: _timescaledb_internal for internal functions.
* _timescaledb_catalog for metadata tables.
* Remove postgres_fdw dependency
* Improve code comments in sql code
