Cleanup & Refactor kClient generators code before migrating to devfile library

[maysunfaisal]

Repo devfile/parser is going to be the home for much of the generator's code that will be used odo, devworkspace operator and console.

The devfile/parser library should be able to generate basic Kubernetes objects from the devfile. The list of these functions and objects can be found documented at the design doc for the library and also the util funcs that can be found in the same doc.

Currently, Odo and Devworkspace operator repo generate their own Kube structs and objects, so there is a lot of redundant code and issue devfile/api#181 will be solving that problem for all the consumers of the devfile/parser.

[maysunfaisal]

Discussed this with @kadel & @mik-dass and we figured this was the best approach for all the parties involved.

[maysunfaisal]

Some comments from @adisky on the doc https://docs.google.com/document/d/1ffLi37fM7LAjRK5SXAw-yVNwr9GchFYy_e_5VD-FOZc/edit#heading=h.v1ex47x85625

To summarize some of the early concerns:

• kclient.GetContainers and GetVolumes should take devfile data obj as input and just return kube structs accordingly
• GeneratePodTemplateSpec() should take all the information and generate the spec rather than passing the object around and adding resources to it later
• kube and common utils have generator functions that should essentially reside in kclient generators