Wallclock BankingStage Throttle (#15731) (#15889)

(cherry picked from commit c1ba265dd9)

Co-authored-by: carllin <carl@solana.com>

sdk/program/src/clock.rs

@@ -6,6 +6,8 @@ pub const DEFAULT_TICKS_PER_SECOND: u64 = 160;
 
 pub const MS_PER_TICK: u64 = 1000 / DEFAULT_TICKS_PER_SECOND;
 
+pub const SLOT_MS: u64 = (DEFAULT_TICKS_PER_SLOT * 1000) / DEFAULT_TICKS_PER_SECOND;
+
 // At 160 ticks/s, 64 ticks per slot implies that leader rotation and voting will happen
 // every 400 ms. A fast voting cadence ensures faster finality and convergence
 pub const DEFAULT_TICKS_PER_SLOT: u64 = 64;