Move default labeller to deploy since it used in deployer.

[tejal29]

Move default labeller to deploy since it used in deployer.

We need this to fetch all the deployments deployed by skaffold for deploy healthcheck. Having this in runner adds a cyclic dependency

[codecov]

Codecov Report

Merging #2335 into master will increase coverage by 0.29%.
The diff coverage is 100%.

Impacted Files	Coverage Δ
pkg/skaffold/deploy/labeller.go	100% <ø> (ø)
pkg/skaffold/runner/runner.go	66.66% <100%> (ø)	⬆️
cmd/skaffold/app/cmd/debug.go	50% <0%> (-4.55%)	⬇️
pkg/skaffold/config/options.go	100% <0%> (ø)	⬆️
pkg/skaffold/kubernetes/port_forward.go
...ffold/kubernetes/portforward/port_forward_entry.go	100% <0%> (ø)
...affold/kubernetes/portforward/forwarder_manager.go	31.57% <0%> (ø)
...g/skaffold/kubernetes/portforward/pod_forwarder.go	87.14% <0%> (ø)
...g/skaffold/kubernetes/portforward/entry_manager.go	100% <0%> (ø)
...affold/kubernetes/portforward/kubectl_forwarder.go	0% <0%> (ø)
... and 3 more