Lint for sum and product in consensus code (#2226)

## Issue Addressed

Closes #1621

## Proposed Changes

Use the `disallowed_method` lint to ban uses of `Iterator::{sum,product}` from `types` and `state_processing`.

## Additional Info

The lint is turned off in the tree hash caching code, as it is performance sensitive and overflowy arithmetic is already allowed there.

consensus/state_processing/src/lib.rs

@@ -1,4 +1,5 @@
 #![deny(clippy::integer_arithmetic)]
+#![deny(clippy::disallowed_method)]
 
 #[macro_use]
 mod macros;