Scanner (#156)

* feat: integrate CancellationToken for unified background services management

- Consolidate data scanner and auto heal cancellation tokens into single unified token
- Move GLOBAL_BACKGROUND_SERVICES_CANCEL_TOKEN to global.rs for centralized management
- Add graceful shutdown support to MRF heal routine with MinIO-compatible logic
- Implement heal_routine_with_cancel method preserving original healing logic
- Update main.rs to use unified background services shutdown mechanism
- Enhance error handling with proper ecstore Result types
- Fix clippy warnings for needless return statements
- Maintain backward compatibility while adding modern cancellation support

This change provides a cleaner architecture for background service lifecycle management
and ensures all healing services can be gracefully shut down through a single token.

Signed-off-by: junxiang Mu <1948535941@qq.com>

* fix: Refact heal and scanner design

Signed-off-by: junxiang Mu <1948535941@qq.com>

* refact: step 2

Signed-off-by: junxiang Mu <1948535941@qq.com>

* feat: refactor scanner module and add data usage statistics

- Move scanner code to scanner/ subdirectory for better organization
- Add data usage statistics collection and persistence
- Implement histogram support for size and version distribution
- Add global cancel token management for scanner operations
- Integrate scanner with ECStore for comprehensive data analysis
- Update error handling and improve test isolation
- Add data usage API endpoints and backend integration

Signed-off-by: junxiang Mu <1948535941@qq.com>

* Chore: fix ref and fix comment

Signed-off-by: junxiang Mu <1948535941@qq.com>

* fix: fix clippy

Signed-off-by: junxiang Mu <1948535941@qq.com>

---------

Signed-off-by: junxiang Mu <1948535941@qq.com>
Co-authored-by: dandan <dandan@dandandeMac-Studio.local>

crates/ahm/src/lib.rs

@@ -0,0 +1,54 @@
+// 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::OnceLock;
+use tokio_util::sync::CancellationToken;
+
+pub mod error;
+pub mod scanner;
+
+pub use error::{Error, Result};
+pub use scanner::{
+    load_data_usage_from_backend, store_data_usage_in_backend, BucketTargetUsageInfo, BucketUsageInfo, DataUsageInfo, Scanner,
+    ScannerMetrics,
+};
+
+// Global cancellation token for AHM services (scanner and other background tasks)
+static GLOBAL_AHM_SERVICES_CANCEL_TOKEN: OnceLock<CancellationToken> = OnceLock::new();
+
+/// Initialize the global AHM services cancellation token
+pub fn init_ahm_services_cancel_token(cancel_token: CancellationToken) -> Result<()> {
+    GLOBAL_AHM_SERVICES_CANCEL_TOKEN
+        .set(cancel_token)
+        .map_err(|_| Error::Config("AHM services cancel token already initialized".to_string()))
+}
+
+/// Get the global AHM services cancellation token
+pub fn get_ahm_services_cancel_token() -> Option<&'static CancellationToken> {
+    GLOBAL_AHM_SERVICES_CANCEL_TOKEN.get()
+}
+
+/// Create and initialize the global AHM services cancellation token
+pub fn create_ahm_services_cancel_token() -> CancellationToken {
+    let cancel_token = CancellationToken::new();
+    init_ahm_services_cancel_token(cancel_token.clone()).expect("AHM services cancel token already initialized");
+    cancel_token
+}
+
+/// Shutdown all AHM services gracefully
+pub fn shutdown_ahm_services() {
+    if let Some(cancel_token) = GLOBAL_AHM_SERVICES_CANCEL_TOKEN.get() {
+        cancel_token.cancel();
+    }
+}