refactor: introduce DdlTaskExecutor and refactor statement executor (#2341)

* feat: add kv store option

* refactor: refactor statement executor

* refactor: refactor standalone table creator

* chore: apply suggestions from CR

* chore: apply suggestions from CR

* refactor: move ShowCreateTable and CreateDatabase to StatementExecutor

* fix: fix RegionDistribution

* feat: build standalone

* chore: apply suggestions from CR

* chore: apply suggestions from CR

* chore: apply suggestions from CR

src/datanode/src/datanode.rs

@@ -33,7 +33,7 @@ use meta_client::MetaClientOptions;
 use mito2::config::MitoConfig;
 use mito2::engine::MitoEngine;
 use object_store::util::normalize_dir;
-use query::QueryEngineFactory;
+use query::{QueryEngineFactory, QueryEngineRef};
 use secrecy::SecretString;
 use serde::{Deserialize, Serialize};
 use servers::heartbeat_options::HeartbeatOptions;
@@ -401,6 +401,7 @@ pub struct Datanode {
     services: Option<Services>,
     heartbeat_task: Option<HeartbeatTask>,
     region_server: RegionServer,
+    query_engine: QueryEngineRef,
     greptimedb_telemetry_task: Arc<GreptimeDBTelemetryTask>,
 }
 
@@ -423,7 +424,7 @@ impl Datanode {
                 .context(RuntimeResourceSnafu)?,
         );
 
-        let mut region_server = RegionServer::new(query_engine, runtime.clone());
+        let mut region_server = RegionServer::new(query_engine.clone(), runtime.clone());
         let log_store = Self::build_log_store(&opts).await?;
         let object_store = store::new_object_store(&opts).await?;
         let engines = Self::build_store_engines(&opts, log_store, object_store).await?;
@@ -454,6 +455,7 @@ impl Datanode {
             services,
             heartbeat_task,
             region_server,
+            query_engine,
             greptimedb_telemetry_task,
         })
     }
@@ -502,6 +504,10 @@ impl Datanode {
         self.region_server.clone()
     }
 
+    pub fn query_engine(&self) -> QueryEngineRef {
+        self.query_engine.clone()
+    }
+
     // internal utils
 
     /// Build [RaftEngineLogStore]