Add k8 style managed by label to skaffold deployed pods

[tejal29]

Fixes #2045

This PR will works with internal metrics gathering logic.

Summary of Changes:

1. Add a labeller to deployer in the Runner so that all the labeller will be propagated to all the deployers.
2. Remove the existing default labels which was only added in deploying with helm deployer.

[codecov-io]

Codecov Report

Merging #2055 into master will increase coverage by 0.05%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #2055      +/-   ##
=========================================
+ Coverage   56.04%   56.1%   +0.05%     
=========================================
  Files         179     180       +1     
  Lines        7742    7750       +8     
=========================================
+ Hits         4339    4348       +9     
+ Misses       2987    2986       -1     
  Partials      416     416

Impacted Files	Coverage Δ
pkg/skaffold/deploy/labels.go	16.04% <ø> (+0.19%)	⬆️
pkg/skaffold/runner/runner.go	64.77% <100%> (+0.2%)	⬆️
pkg/skaffold/runner/labeller.go	100% <100%> (ø)

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[priyawadhwa]

LGTM