JDBC drivers are transitively inherited although declared optional

The JDBC driver dependencies are declared optional (HIVE-25701) because we don't really need them and it is up to the end-user to decide which DBMS they will use and pick the appropriate driver for their use case.

Also declaring them as optional should stop their transitive propagation to 3rd-party projects that depend on Hive modules.

Currently the optional declaration is in the respective dependencyManagement sections of the project:

• https://github.com/apache/hive/blob/dd8a867386b605ecd7e8dbec476556bf24f54c6f/pom.xml#L1323
• https://github.com/apache/hive/blob/dd8a867386b605ecd7e8dbec476556bf24f54c6f/standalone-metastore/pom.xml#L352

However due to MNG-5227, the optional declaration in the dependencyManagement has no effect so JDBC dependencies are transitively propagated to every module that depends on some Hive module with a JDBC driver dependency.

Till MNG-5227 is fixed we will need to include optional in every explicit declaration of the dependency.