This PR introduces new functionality for running e2e-tests in
k8s-cluster.
`make test` from a root invokes deploying of new sandbox for testing
cozystack.
from `packages/core/testing`:
`make test` - runs the end-to-end tests.
`make exec` - opens an interactive shell in the sandbox container.
`make login` - downloads the kubeconfig into a temporary directory and
runs a shell with the sandbox environment; mirrord must be installed.
`make proxy` - enables a SOCKS5 proxy; mirrord and gost must be
installed.
Signed-off-by: Andrei Kvapil <kvapss@gmail.com>