Removes the last remaining server dependencies from jdbc client. In order to do that it introduces the new project sql-shared-proto that contains only XContent-serializable classes. HTTP Client and JDBC now depend only on sql-shared-proto. I had to keep the original sql-proto project since it is used as a dependency by sql-cli and security integration tests.
Relates #29856
This commit makes x-pack a module and adds it to the default
distrubtion. It also creates distributions for zip, tar, deb and rpm
which contain only oss code.