The protocol now allows protocol modules to return JSON formatted
information about the protocol module internals. Currently this is only
implemented by the mariadbbackend module and it returns the current
connection ID on the backend server.
Removed unused and properly documented all entry points in the protocol
module API. As the removal of the `session` entry point is an backwards
incompatible change, the protocol API version was updated.
Session commands that span multiple packets are now allowed and will
work. However, if one is executed the session command history is disabled
as no interface for appending to session commands exists.
The backend protocol modules now also correctly track the current
command. This was a pre-requisite for large session commands as they
needed to be gathered into a single buffer and to do this the current
command had to be accurate.
Updated tests to expect success instead of failure for large prepared
statements.
