show kube config path in preferences

[xtreme-vikram-yadav]

What this PR does / why we need it: This PR assists the user in finding the local path to kube config which is used by octant. It is useful is case when the user has uploaded the config manually via loading api and a temporary kube config file is created and stored in the temp directory.

Which issue(s) this PR fixes

• Fixes Kubeconfig location on windows #1893

Special notes for your reviewer:
Steps for reproduction/acceptance:

Given kube config exists in a default location(~/.kube/config)
When the user starts octant
And the user opens preferences
Then the user sees the local kube config path with icon to copy to clipboard

Given kube config does not exist in a default location(~/.kube/config)
When the user starts octant
And the user pastes the kube config in the modal
And the user opens preferences
Then the user sees the local kube config path with icon to copy to clipboard

Some implementation decisions:

The octant.generator interface now returns multiple events which extends a *_manager's capability to perform multiple small computations and stream back multiple results as events. A managers setup is an overkill for implementing small features. This approach helps with testing by keeping the handlerFunc usage the same as before and avoids generator classes doing duplicated work.

[mklanjsek]

I am not sure if this is the bast way to solve the problem from user experience point of view. Maybe just making kube.config location directly configurable from preferences would be better and in the same time it would allow users to switch between different configurations. We should probably discuss it as a team.

[xtreme-vikram-yadav]

I created #2497 to allow users to upload their kube config.

[mklanjsek]

Looks good! You'll need to regenerate mock files before merging.

[xtreme-vikram-yadav]

I think it's an environment thing where there are differences in the go generate output. I'll use a linux machine this time to fix it and think of a long term solution to notify of the version differences for tools like mockgen and goimports in the CI.