refactor: Restructure project layout and clean up dependencies (#30)

This commit introduces a significant reorganization of the project structure to improve maintainability and clarity.

Key changes include:
- Adjusted the directory layout for a more logical module organization.
- Removed unused crate dependencies, reducing the overall project size and potentially speeding up build times.
- Updated import paths and configuration files to reflect the structural changes.

crates/s3select-api/src/query/scheduler.rs

@@ -0,0 +1,46 @@
+// Copyright 2024 RustFS Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::sync::Arc;
+
+use async_trait::async_trait;
+use datafusion::common::Result;
+use datafusion::execution::context::TaskContext;
+use datafusion::physical_plan::{ExecutionPlan, SendableRecordBatchStream};
+
+pub type SchedulerRef = Arc<dyn Scheduler + Send + Sync>;
+
+#[async_trait]
+pub trait Scheduler {
+    /// Schedule the provided [`ExecutionPlan`] on this [`Scheduler`].
+    ///
+    /// Returns a [`ExecutionResults`] that can be used to receive results as they are produced,
+    /// as a [`futures::Stream`] of [`RecordBatch`]
+    async fn schedule(&self, plan: Arc<dyn ExecutionPlan>, context: Arc<TaskContext>) -> Result<ExecutionResults>;
+}
+
+pub struct ExecutionResults {
+    stream: SendableRecordBatchStream,
+}
+
+impl ExecutionResults {
+    pub fn new(stream: SendableRecordBatchStream) -> Self {
+        Self { stream }
+    }
+
+    /// Returns a [`SendableRecordBatchStream`] of this execution
+    pub fn stream(self) -> SendableRecordBatchStream {
+        self.stream
+    }
+}