Errors don't surface when starting a consumer fails to authenticate

[angelozerr]

Errors don't surface when starting a consumer fails to authenticate

Fixes #104

Signed-off-by: azerr [email protected]

[angelozerr]

This PR improves the start / stop consumer:

• by managing state launch (starting, started, stopping, stopped) which is used by code lens (ex : when a consumer is starting,the start and stop lenses are not displayed)
• by executing start / stop consumer with progress. It's very helpful when you start a consumer in a cluster which cannot be accessed (you see on the bottom of vscode the progress state)
  
• display error when start consumer cannot be executed (ex : cluster cannot be accessed)
• improve consumer view to display consumer options when it is started + display error

[fbricon]

Thanks @angelozerr!