Remove credit types from Params

[technicallyty]

Summary

following #1015 we should remove credit types from params.

Problem Definition

once #1015 is merged, we will have support for credit types in ORM. We will no longer need them in x/params

Proposal

• remove credit types from params code
• update submodule code / util functions to fetch credit types from ORM, not x/params keeper.
• update tests to not use mock param keeper for credit types (we can just put them in ORM table)
• gov handler CLI integration test
• add code to migration to move any existing credit types into ORM storage

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