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. Changed default behavior to use a single dispatcher.
Would be good to define this version as a property as the same dependency is used iin multiple places (but you can do it in a separated PR if you want)