GitOps Toolkit documentation on combining packages to build better controllers

[scottrigby]

As part of unifying standards for Flux controllers – and any controllers build on the GitOps Toolkit – we want to update our existing documentation to tells people how to combine our packages to build better controllers.

Goals:

• We should provide in-depth guidance on why you should do things in a certain way
• This will be an effort to replace existing docs at https://fluxcd.io/docs/gitops-toolkit/
• https://fluxcd.io/docs/gitops-toolkit/packages/ Remove CRUD example at the bottom of this page.
• https://fluxcd.io/docs/gitops-toolkit/source-watcher/ should explain the broader picture. More like a reference document with human explanation, and link to a full blown example. Currently it feels like a tutorial which doesn’t cover the whole subject