feat: Implementing cross-segment read/write for WAL based on local di…

…sk (#1556)

## Rationale
Improving WAL based on local disk.

This is a follow-up task for #1552.

## Detailed Changes
1. Make MAX_FILE_SIZE configurable.
2. Allocate enough space when creating a segment to avoid remapping when
appending to the segment.​
3. Add `MultiSegmentLogIterator` to enable cross-segment reading.
4. When writing, if the current segment has insufficient space, create a
new segment and write to the new segment.​

## Test Plan
Unit test.

src/wal/src/local_storage_impl/config.rs

@@ -20,7 +20,7 @@ use serde::{Deserialize, Serialize};
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct LocalStorageConfig {
     pub path: String,
-    pub max_segment_size: u64,
+    pub max_segment_size: usize,
     pub cache_size: usize,
 }
 

src/wal/src/local_storage_impl/record_encoding.rs

@@ -62,6 +62,7 @@ define_result!(Error);
 /// |  (u8)   | (u32)  | (u32)  |   (u64)    |    (u64)     |     (u32)    |       |
 /// +---------+--------+--------+------------+--------------+--------------+-------+
 /// ```
+#[derive(Debug)]
 pub struct Record<'a> {
     /// The version number of the record.
     pub version: u8,
@@ -183,6 +184,13 @@ impl RecordEncoding {
 
         // Read length
         let length = buf.try_get_u32().context(Decoding)?;
+        ensure!(
+            length > 0,
+            LengthMismatch {
+                expected: 1usize,
+                actual: 0usize
+            }
+        );
 
         // Ensure the buf is long enough
         ensure!(