fix: get table size from metadata, not files (#3790)

Some issues:
- file_size_bytes is optional in the manifest, so if it's not there (old
writer I guess) it'll under-report the table size.
- it changes results a little bit from the old way by including per-file
footers and metadata (probably not a big difference at real scale)

---------

Co-authored-by: Will Jones <willjones127@gmail.com>

nodejs/__test__/table.test.ts

@@ -277,8 +277,16 @@ describe.each([arrow15, arrow16, arrow17, arrow18])(
         },
         numIndices: 0,
         numRows: 3,
-        totalBytes: 44,
+        // Full on-disk size of the two data files, footers and metadata included.
+        totalBytes: 684,
       });
+
+      // Index files count toward totalBytes too (only deletion files and
+      // manifests are excluded).
+      await table.createIndex("id", { config: Index.btree() });
+      const statsWithIndex = await table.stats();
+      expect(statsWithIndex.numIndices).toBe(1);
+      expect(statsWithIndex.totalBytes).toBeGreaterThan(684);
     });
 
     it("should overwrite data if asked", async () => {

nodejs/src/table.rs

@@ -1043,7 +1043,10 @@ impl From<lancedb::index::IndexStatistics> for IndexStatistics {
 
 #[napi(object)]
 pub struct TableStatistics {
-    /// The total number of bytes in the table
+    /// The total size, in bytes, of the table's data files, index files, and
+    /// overlay files
+    ///
+    /// Read from the manifest, so this excludes deletion files and manifests.
     pub total_bytes: i64,
 
     /// The number of rows in the table