chore: add / refactor dev commands

[bshaffer]

Big Changes

• Adds a new script to add a component (dev/google-cloud add-component)
• Adds a new script to list details of a component or all components (dev/google-cloud component-info)
• Adds Component class for listing all details about a given component (used for docs, release script, and component info command)
• Adds NewComponent class which determines expected names / paths for a new component based on the proto service file (used by new-component command).
• Fixes release notes

Other refactorings!

• Deleted manifest.json
• Deleted the entire docs/ directory
• Moved all dependencies used only for dev into dev/composer.json
• Adds specific test workflow for dev which runs on 8.0 only
• Refactors and simplifies old AddComponent command (uses twig, removes a lot of unnecessary logic)
• Refactors github actions workflows for docs and lint into separate configuration files.
• Removes old commands which are no longer used (Credentials command, ComponentIntegration command)

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[vishwarajanand]

Lgtm