jdbc: Support read only connection

[nicktorwald]

Implement both Connection.isReadOnly and Connection.setReadOnly methods.
We need at least Tarantool DB support for that. It seems it should be implemented as part of transaction support how it has already done in Postgres (docs).

For instance, Postgres driver executes SET SESSION CHARACTERISTICS AS TRANSACTION READ ONLY when a read-only flag is set.

[Totktonada]

It is the session parameter and I see no connection with transactions here. Anyway, we cannot implement it right now, so I filed the issue to tarantool and leave the milestone here as is for now. Let's return here when the issue in tarantool will be resolved.

Blocked by tarantool/tarantool#4205