Classic confinment for kubectx snap

Whilst this request looks very similar to historical requests such as Classic confinement for fluxctl and Classic confinement for kontena-lens - I notice one particular difference - those required access to execute arbitrary binaries to authenticate - whereas in this case we seem to only need to perhaps read various files.

As such, if these are always common paths which are used (as was the case with Fluxctl personal-files [Was: Fluxctl snap wants to be classic]) then I think personal-files would be appropriate - since it allows to declare just access to these specific paths and be granted those and still then retain the benefits of isolation from the rest of the system.

@mhalano since it looks like these paths are always in the same sorts of locations (ie. ~/.minikube etc) then I think this would be more appropriate.