Add cleanup function to get rid of hash_type usage

[schuylermartin45]

We do something similar in crm convert. We need to be able to handle recipes that define and use the hash_type variable as some obnoxious to set the /source/sha256 field:

source:
  {{ hash_type }}: {{ hash }}

This makes it impossible to edit the recipe file and should be forbidden. We should correct this to:

source:
  sha256: {{ hash }}