Threadpool2 (#15151) (#15159)

* rework thread pool for hash calculation

* rename

(cherry picked from commit fbf9dc47e9)

Co-authored-by: Jeff Washington (jwash) <75863576+jeffwashington@users.noreply.github.com>

core/src/validator.rs

@@ -1056,7 +1056,7 @@ fn new_banks_from_ledger(
             None,
             &snapshot_config.snapshot_package_output_path,
             snapshot_config.archive_format,
-            &bank_forks.root_bank().get_thread_pool(),
+            Some(&bank_forks.root_bank().get_thread_pool()),
         )
         .unwrap_or_else(|err| {
             error!("Unable to create snapshot: {}", err);