Clean up solution in walking skeleton initial implementation and merge to upstream

[garagatyi]

Issue problem:
We have working plugin broker integrated with Che master in a branch. We need to merge this upstream to continue our iterative approach of delivering Walking skeleton and Che 7 experience to Che default assembly and RhChe on OSIO.
This issue doesn't include improvements and fixes that we need in that initial implementation. Those tasks would be solved as separate issues.

This issue would deliver Walking skeleton flow after broker updates are also done.
This issue will solve next issues:

• Download Che Plugins and Editor meta.yaml and invoke Che Plugin Broker Delivering of ChePlugins binaries to the editor container eclipse-che/che#10561
• Update Che workspace config model: replace Feature/CheService with ChePlugin Rework Workspace.Next services/features to ChePlugin model eclipse-che/che#10202

Red Hat Che version:

version: (help/about menu)

• I can reproduce it on latest official image

Reproduction Steps:

Describe how to reproduce the problem

Runtime:

runtime used:

• minishift (include output of minishift version)
• OpenShift.io
• Openshift Container Platform (include output of oc version)
• k8s (include output of kubectl version)