feat: support trigger drop (#248)

* feat: add trigger-drop proto

* remove trigger id of DropTriggerExpr

proto/greptime/v1/ddl.proto

@@ -326,3 +326,9 @@ message WebhookOptions {
     string url = 1;
     map<string, string> opts = 2;
 }
+
+message DropTriggerExpr {
+    string catalog_name = 1;
+    string trigger_name = 2;
+    bool drop_if_exists = 3;
+}

proto/greptime/v1/meta/ddl.proto

@@ -88,6 +88,10 @@ message CreateTriggerTask {
     CreateTriggerExpr create_trigger = 1;
 }
 
+message DropTriggerTask {
+    DropTriggerExpr drop_trigger = 1;
+}
+
 message DdlTaskRequest {
     RequestHeader header = 1;
     QueryContext query_context = 64;
@@ -108,6 +112,7 @@ message DdlTaskRequest {
         DropViewTask drop_view_task = 14;
         AlterDatabaseTask alter_database_task = 15;
         CreateTriggerTask create_trigger_task = 16;
+        DropTriggerTask drop_trigger_task = 17;
      }
 }