[Feature] Add support for GKEStartPodOperator (again)

[burbanom]

Description

Like already suggested in Add support for GKEStartPodOperator #455. I have already been working on this subject and I have a working version. I also have a GKE version of watcher execution mode.

Use case/motivation

Better integration with GKE

Related issues

#455

Are you willing to submit a PR?

• Yes, I am willing to submit a PR!

[tatiana]

That's exciting, @burbanom , thank you - we're looking forward to seeing your contribution!