Write a guide for plugin authors that need to refactor due to removing node-level config

**Why**: Sub of #765
**What**: Write update-guide for plugins builders that need to refactor our node level config
**Context**
We are removing node-level config from our builtins and removing the related logic from IF. There are some third party plugins out there that use node-level config, which will have to be refactored to accept what was node-level config from global config or inputs. We should provide a walkthrough guide for how to do this refactoring to make it as easy for people as possible.

Blocked by #775, #776, #777

**Scope of work**:
- [ ] write a plugin refactor guide for plugins that use node-level config

**Acceptance criteria**
- [ ] there is a guide for refactoring plugins to remove node-level config available in our github repository and linked to from our README