IGNITE-22000 Get rid of unnecessary conversion of DDL commands

[xtern]

https://issues.apache.org/jira/browse/IGNITE-22000

• DdlSqlToCommandConverter now converts AST nodes not to DDLCommand but to CatalogCommand
• Removed DdlToCatalogCommandConverter and all related to DDLCommand classes.
• Reworked related tests and removed DistributionZoneDdlCommandHandlerTest because it is now looks useless

Separate issue about handling ifExists flag inside command will be created, because it requires a lot of additional changes and current PR is big enough