Remove/Hide "Code Plugins" integration

Remove from display and API.

Since Feb 2017 code plugin integrations are not supported by Red Hat. We want to remove this option from the UI (" Your_API > Integration > Configuration > Edit integration settings").

On-prem: Remove the whole "Plugin" integration option in the next release.

SaaS: Hide the "Plugin" section to new or existing services that doesn't have this option selected. For services making use of this kind of integration:

• Show the plugin section but do not allow choosing another code plugin integration (allow only changing to Gateway or Service Mesh integrations)
• Show a message in the UI indicating that the code plugin integration is unsupported.
• If the user select another integration method, show a message indicating that he/she would not be able to select a code plugin again.

UPDATE: Please note that the "REST integration" querying the 3scale APIs continues to be fully supported so we will need to move it to another section.

This include rolling update and cucumbers.