[Broker-J] Jetty server dependencies update

Jetty Server 9.x has reached end of community support (github issue). Current Jetty version should be updated either to 10.x or 11.x. Considering that Jetty 12.x is currently in alpha version, it would be preferable to update it to the latest version available (11.x) to make easier further updates.

Update will include

• dependencies update
• namespaces update (javax.servlet.* migrated to jakarta.servlet.*)
• code refactoring (in few cases it may be needed to refactor logic in favor of more actual Jetty mechanisms)