Process additional fields in meta.yaml

[garagatyi]

Description:
See detailed explanation here eclipse-che/che#12908 (comment)

Flow:

• Add apiVersion field to meta.yaml model
• In case apiVersion: 2 do:
  • Unified broker should be able to parse and process new fields (inside of spec field) of meta.yaml and not process deprecated fields (extensions, attributes, url). See example here https://gist.githubusercontent.com/garagatyi/0ae0f6a05b76e504c9152e6eef160917/raw/meta.yaml
  • For VS Code plugins also process extensions field, see https://gist.githubusercontent.com/garagatyi/0ae0f6a05b76e504c9152e6eef160917/raw/plugin-vscode-with-ram.yaml
  • For Theia plugins process plugins field instead of extensions in VS Code plugin case. Limit to support of 1 plugin since multiple plugins support can bloat the implementation, which is not needed at this point.
• In case apiVersion: 1: fail - should be tackled in Add unified plugin broker compatibility with the old meta.yaml flow #1310

Related to eclipse-che/che#12908

[amisevsk]

@ibuziuk I'm closing this issue as fixed in eclipse-che/che-plugin-broker#55, please reopen if this is inaccurate (I wasn't around for planning this sprint)