snapshots: serialize version file first (#27192)

serialize version file first

(cherry picked from commit c1111fa)

runtime/src/snapshot_utils.rs

@@ -344,10 +344,12 @@ pub fn archive_snapshot_package(
 
         let do_archive_files = |encoder: &mut dyn Write| -> Result<()> {
             let mut archive = tar::Builder::new(encoder);
+            // Serialize the version and snapshots files before accounts so we can quickly determine the version
+            // and other bank fields. This is necessary if we want to interleave unpacking with reconstruction
+            archive.append_path_with_name(staging_dir.as_ref().join("version"), "version")?;
             for dir in ["snapshots", "accounts"] {
                 archive.append_dir_all(dir, staging_dir.as_ref().join(dir))?;
             }
-            archive.append_path_with_name(staging_dir.as_ref().join("version"), "version")?;
             archive.into_inner()?;
             Ok(())
         };