Fixed multi-threaded sync + related improvements

-The block_parallel_tasks feature has been improved and fixed so that it is now safe to cancel (Ctrl+C) or kill (kill cmd not kill -9) the task and resume the sync later without missing transactions. The new block_parallel_tasks default is 8 threads which seems to be the sweet spot for any type of cpu
-Numerous improvements to the benchamark script to utilize new benchmark settings, auto-add credentials to the benchmark database, reuse the same sync code as the regular block sync instead of using a copy of the code and more
-Added a new cmd to run the benchmark script `npm run benchmark`
-README updated to include the new benchmark script instrutions + include multi-threaded sync as a feature

package.json

@@ -27,7 +27,8 @@
     "create-backup": "node ./scripts/create_backup.js",
     "restore-backup": "node ./scripts/restore_backup.js",
     "delete-database": "node ./scripts/delete_database.js",
-    "update-explorer": "node ./scripts/update_explorer.js"
+    "update-explorer": "node ./scripts/update_explorer.js",
+    "benchmark": "node ./scripts/benchmark.js"
   },
   "dependencies": {
     "async": "^3.2.4",