Add support for prepared statements in JDBC

[ohadzeliger]

This PR enables support for prepared statements on the JDBC server.
Specifically, support for PreparedStatement setObject() and setArray().
Also, JDBCRelationalConnection needed support for array creation.
A slew of type conversion utilities were added in support of these features.
In general, we have 3 models that we are dealing with:

• Java (including primitives, [], null)
• JDBC (including primitive, Array, Struct, NULL)
• Protobuf

And because of the way the API is structured, we may need to perform conversions between all 3. Specifically, we support the following:

• Java and SQL primitives are treated the same way
• Java arrays are only supported in Connection.createArrayOf, where the type of array elements is also provided
• SQL Array and Struct are assumed in all cases of nesting. That is, an array of elements would be assumed to have SQL Array if there is any nested array. The reasoning is that we would need the additional type information in these cases
  Some cleanup and restructuring of that code may be warranted, in addition to null, error and edge case testing.

The protobuf for the Array definition was changed in order to support the extra type information. This causes version incompatibility with the previous version so multi-server tests for arrays needed to be excluded. Another option would have been to replicate the array definition for backwards compatibility but that would have added tech debt to the system.