Fix Rust beta compiler errors 1.78.0-beta.1 (#5439)

* remove redundant imports

* fix test

* contains key

* fmt

* Merge branch 'unstable' into fix-beta-compiler

common/slot_clock/src/manual_slot_clock.rs

@@ -1,6 +1,5 @@
 use super::SlotClock;
 use parking_lot::RwLock;
-use std::convert::TryInto;
 use std::sync::Arc;
 use std::time::Duration;
 use types::Slot;