Parameter substitution in text protocol

The current implementation of parameter substitution (text protocol) is written in pure Python and is too slow, compared to other MariaDB Connectors.

Instead, parameter substitution should be handled in C code.

In order to avoid unnecessary memory consumption, this should ideally be implemented using a (not yet existing) stream send function.

The send function could be implemented in Connector/C or as a fallback in Connector/Python by writing directly to the socket (which can be obtained via the C/C API).