DROP sharded table

[donhardman]

We should add functionality to support dropping shared tables. The command should clean up everything associated with the shared table. To make this happen, we should start with a special command DROP SHARDED TABLE. After that, we'll migrate to use the DROP TABLE command, while the daemon should detect if it's a shared table or not and process the request accordingly.

This requires modifications on the daemon side, so we'll start with the DROP SHARDED TABLE syntax first.

[donhardman]

It was implemented in these two pull requests:

• Add possibility to drop sharded table #354
• Deprecate global hooks and refactor Pluggable system buddy-core#71

During the implementation of the DROP SHARDED TABLE logic, a requirement also arose to refactor our old system with hooks. As a result, I made changes in the core and placed code in the appropriate locations. The QueryProcessor is now much cleaner, and the common logic for using processors of each plugin has become clearer.

[donhardman]

Merged into the main.

@PavelShilin89 let's add tests.

We should cover that DROP SHARDED TABLE x works fine for both single sharded and clustered environment.

That means just implement various check that executes DROP SHARTED TABLE x for different tables (also not sharded) and make sure that it works ONLY for those that sharded