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>

accounts-bench/src/main.rs

@@ -1,3 +1,4 @@
+#![allow(clippy::integer_arithmetic)]
 #[macro_use]
 extern crate log;
 use clap::{crate_description, crate_name, value_t, App, Arg};