feat: Add DropTableTask, AlterTableTask (#54)

* feat: use type instead of pb bytes

* feat: add table_info to CreateTableTask

* fix: remove unused fields

* feat: bring create route method back

* feat: add table_id in SubmitDdlTaskResponse

* feat: add drop table task

* feat: add alter table task

* chore: allow large_enum_variant

* chore: apply suggestions from CR

src/lib.rs

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 mod serde;
+#[allow(clippy::large_enum_variant)]
 pub mod v1;
 
 pub mod prometheus {