Upgrade Rust to 1.52.0 (#17096)

* Upgrade Rust to 1.52.0
update nightly_version to newly pushed docker image
fix clippy lint errors
1.52 comes with grcov 0.8.0, include this version to script

* upgrade to Rust 1.52.1

* disabling Serum from downstream projects until it is upgraded to Rust 1.52.1

local-cluster/src/cluster_tests.rs

@@ -384,7 +384,7 @@ fn get_and_verify_slot_entries(
     last_entry: &Hash,
 ) -> Vec<Entry> {
     let entries = blockstore.get_slot_entries(slot, 0).unwrap();
-    assert_eq!(entries.verify(last_entry), true);
+    assert!(entries.verify(last_entry));
     entries
 }