Refactor canvas and component specs

[begelundmuller]

• Removes support for data: properties in the component YAML
• Changes the ResolveComponent RPC to only resolve templating in the renderer properties
• Removes the already deprecated components/{name}/data endpoint
• As a small affordance for better error messages, if a component's renderer properties contains a metrics_view key, it add it to the component's refs
• (New) Removed gap and column from the canvas YAML
• (New) Added max_width to the canvas YAML
• (New) Added theme to the canvas YAML with the same behavior as in the explore YAML
• (New) Removed exceptional handling for vega_lite, moved its validation to component-template-v1.json

Closes #5892

[begelundmuller]

Marking this PR as draft pending finalization of the new semantics for canvas dashboards. @djbarnwal will follow up.