Repair pysqlcipher and use sqlcipher3

Repair pysqlcipher and use sqlcipher3

The ``pysqlcipher`` dialect now imports the ``sqlcipher3`` module
for Python 3 by default.    Regressions have been repaired such that
the connection routine was not working.

To better support the post-connection steps of the pysqlcipher
dialect, a new hook Dialect.on_connect_url() is added, which
supersedes Dialect.on_connect() and is passed the URL object.
The dialect now pulls the passphrase and other cipher args
from the URL directly without including them in the
"connect" args.  This will allow any user-defined extensibility
to connecting to work as it would for other dialects.

The commit also builds upon the extended routines in
sqlite/provisioning.py to better support running tests against
multiple simultaneous SQLite database files.  Additionally enables
backend for test_sqlite which was skipping everything
for aiosqlite too, fortunately everything there is passing.

Fixes: #5848
Change-Id: I43f53ebc62298a84a4abe149e1eb699a027b7915