Update ZIO SQL to use ZIO JDBC

[jdegoes]

ISSUE

ZIO SQL was created before ZIO JDBC, and as a result, had to re-create some low-level interface to JDBC, including an asynchronous connection pool, and ZIO wrappers around JDBC machinery.

SOLUTION

In order to minimize code duplication and to promote ZIO JDBC as the foundation of RDMBS libraries in the ZIO ecosystem, we should upgrade ZIO SQL to use ZIO JDBC.

IMPACT

Making this change will make maintenance of this project much easier, because it will mean that JDBC functionality does not have to be replicated in this project. In addition, it means that future upgrades to ZIO JDBC will automatically benefit ZIO SQL, creating a higher-quality library with many more features that users will appreciate.

WHERE TO LOOK

Look at the jdbc top-level directory, which contains the subproject for JDBC integration. The TransactionModule can be implemented directly atop ZIO JDBC, and older wrappers and connection pools deleted.

PROBLEMMATIC ISSUES

ZIO JDBC has not yet had a first release yet, so in order to perform this upgrade, it may be necessary to (a) get a first release out of ZIO JDBC, or (b) use SBT source dependency to depend upon a particular Git hash of ZIO JDBC.