Create random binary command (#13542)

# Description/User-Facing Changes

Creates a new `random binary <LENGTH>` command, which returns random
bytes.

Resolve #13500

crates/nu-command/src/default_context.rs

@@ -397,6 +397,7 @@ pub fn add_shell_command_context(mut engine_state: EngineState) -> EngineState {
             RandomFloat,
             RandomInt,
             RandomUuid,
+            RandomBinary
         };
 
         // Generators