Develop technical plan for DevWorkspaceCRD introducing

[sleshchenko]

Is your task related to a problem? Please describe.

DevWorkspaceCRD already has some initial implementation/draft proposal https://github.com/che-incubator/devworkspace-api
It's needed to learn more about it and develop some technical plan how to can move K8s/OS infrastructure to DevWorkspace Controller.

More see epic #15425

[sleshchenko]

During this task several improvements were made:

• Some initial refactoring and improvements are made This PR adds initial improvements that allow developer easier to start devfile/devworkspace-operator#3
• Project now uses Go Modules instead of Go Dep as dependencies manager Migrate to Go modules  devfile/devworkspace-operator#4
• Operator Framework was updated to v0.12.0 Update operator framework to v0.12.0 devfile/devworkspace-operator#5

Also, working on this issue gave a bigger picture of what we have now but I believe it's not time where we can define full and detailed enough technical plan for DevWorkspaceCRD.
So, the current priority is to adapt DevWorkspace Controller to CloudShell needs, some of needed issues are already created under the following epic: #15434
And we'll extend this list later.
So, we're focusing on CloudShell needs but keep in mind the future of DevWorkspace in general, but plan how we can replace K8s infrastructure with DevWorkspace Controller will be made later.