Add hook_scramble

Follow-up to #2610146: Create API for scrambling methods

Problem/Motivation

In order for other contributed modules to hook into the scrambling module and make sure that it's scrambling is done on execution of the scrambling procedure we need a hook_scramble.

Proposed resolution

Create hook_scramble
Create test module in order to use the hook

API changes

Create hook_scramble so that contrib modules can use this hook.