MULE-7545 Refactor AbstractConnector to allow for connectors that don't use default dispatcher pool
(cherry picked from commit c944d18)
MULE-7729: Possible deadlock when handling concurrent requests in a transaction with more than one outbound endpoint

Added a system property to define whether the JdbcConnector will use a pool of dispatcher objects or will use a single dispatcher per endpoint.

(cherry picked from commit 1d58520e5cce8700ef1c34c2448e55ec4ab7b749)