First step towards denying clippy::integer_arithmetic (bp #15366) (#15381)

* CI: Globally deny clippy::integer_arithmetic lint

(cherry picked from commit 7035e8485c)

* Re-allow clippy::integer_arithmetic at crate-level

(cherry picked from commit 7f7370c306)

# Conflicts:
#	bench-tps/tests/bench_tps.rs

Co-authored-by: Trent Nelson <trent@solana.com>

runtime/src/lib.rs

@@ -1,4 +1,5 @@
 #![cfg_attr(RUSTC_WITH_SPECIALIZATION, feature(specialization))]
+#![allow(clippy::integer_arithmetic)]
 pub mod accounts;
 pub mod accounts_background_service;
 pub mod accounts_cache;