Call beginRequest and endRequest

[jeandelavarene]

JDBC 4.3 added two new methods beginRequest -- and endRequest that connection pools can call to demarcate request boundaries.
As the JavaDoc explains, these methods are hints to the driver that a connection becomes active. What the driver does about it is vendor specific. It may not do anything.
This issue is filed to make HikariCP call beginRequest when a connection is borrowed and endRequest when the connection is released.