Support kubernetes executor

[tan-wei-xin-alez]

Is your feature request related to a problem? Please describe.
As mentioned in this issue and this issue, it would be nice to have gitlab's kubernetes executor supported along with its docker executor since both do benefit from not having to push to test job changes

Describe the solution you'd like
I'm not too familiar with the internals of gitlab-ci-local so I am assuming it is non-trivial to support another executor, but the end result would probably be a CLI option or parameter which users can utilize to switch between executors (since I don't think there's a .gitlab-ci.yml keyword that allows specifying whether to use the kubernetes or docker executor unlike with the shell and image keywords unless I'm mistaken?)

Describe alternatives you've considered
Currently, the only alternatives I've considered are changing the original job so that it works with the docker executor (not ideal since it may mask some other bug) or simply pushing the changes to test (which usually takes more time than testing with gitlab-ci-local)

Additional context
Even if this takes a long time to implement, I think it's worth keeping the issue open since others may bump into similar issues and not realize it is a problem with the kubernetes executor not being supported

[elafontaine]

you do know that the kubernetes executor require the whole KUBE_CONFIG to be working, right ?

The way it works with gitlab is that the "tag" on the job decide what runners can be used. The "image" section give the "runtime" to use. The rest should be pretty much transparent for executors... So at this point, I don't believe the kubernetes-executor should be different from the docker-executor.

This is just an opinion as I don't believe we should leak implementation details of gitlab on gitlab-ci-local...