Remove deprecated features: zenml deploy and zenml <stack-component> deploy

[stefannica]

Describe changes

This PR removes the deprecated features that were used to deploy ZenML servers and ZenML stacks and stack components straight from the ZenML CLI. These are now replaced by one-click stack deployments and Terraform stack deployment modules. Mentions to the external mlstacks project are kept or even added as an alternative for now.

Docs are rendered here: https://zenml-io.gitbook.io/stefan-docs

Breaking Changes

This PR removes the following CLI commands and the functionality associated with them:

• zenml deploy
• zenml destroy
• zenml stack recipe *
• zenml stack deploy_mlstack
• zenml stack destroy
• zenml <stack-component> deploy
• zenml <stack-component> destroy

Pre-requisites

Please ensure you have done the following:

• I have read the CONTRIBUTING.md document.
• If my change requires a change to docs, I have updated the documentation accordingly.
• I have added tests to cover my changes.
• I have based my new branch on develop and the open PR is targeting develop. If your branch wasn't based on develop read Contribution guide on rebasing branch to develop.
• If my changes require changes to the dashboard, these changes are communicated/requested.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Other (add details above)

[strickvl]

Good we're finally doing it. Some care will have to be take how we frame it in the release notes, but otherwise aside from the one nit I found, LGTM.

[wjayesh]

can we move this to the same level as the secret-management.md file (that is, directly under deploying-zenml)? this section (manage-the-deployed-services) shouldn't exist anymore. in the toc.md, it is already positioned so.

[wjayesh]

you would then also have to update the path in the toc.md file to the parent directory. Thank you for fixing my oversight! :)

[stefannica]

Done 👍

[wjayesh]

good to go save for a small restructuring