Add unified plugin broker compatibility with the old meta.yaml flow

[garagatyi]

Description:
#1308 is suppose to add extended meta.yaml support when apiVersion: 2. For simplicity and iterability backward compatibility with apiVersion: 1 can be tackled in separate, this, issue.

Flow:
In case apiVersion: 1 or empty (suppose string value) or field is missing convert old meta.yaml flow to apiVersion: 2 representation and proceed with processing as in apiVersion: 2 case.

• Che plugin type only related:
  • Download file by URL from field url in meta.yaml. It can be meta.yaml content or tar.gz archive with it.
  • Remove files copying functionality in common Che plugin type since it is unused.
• VS Code/Theia plugin types: convert apiVersion: 1 model to apiVersion: 2 which is very easy:
  • if meta.attributes.containerImage is present add container entry with image
  • move meta.extensions to meta.spec.extensions for VS Code
  • put meta.extension to meta.spec.extensions for VS Code
  • put meta.url to meta.spec.extensions for VS Code
  • put meta.url to meta.spec.extensions for Theia plugins

Depends on #1308

Related to eclipse-che/che#12908

[garagatyi]

We discussed this with Mario and Ilya and agreed not to support backward compatibility yet since Che is in beta and not heavily used at the moment.

@ibuziuk can we close this issue?

[ibuziuk]

yes, I believe we can close it now