Move bazel code into plugins directory

[priyawadhwa]

Refactoring to move as much bazel code into the plugins directory as possible, so it should be easier to remove the old local builder later on.

continues work on #1765

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@b76ff3c). Click here to learn what that means.
The diff coverage is 14.92%.

@@            Coverage Diff            @@
##             master    #1707   +/-   ##
=========================================
  Coverage          ?   46.07%           
=========================================
  Files             ?      134           
  Lines             ?     6366           
  Branches          ?        0           
=========================================
  Hits              ?     2933           
  Misses            ?     3132           
  Partials          ?      301

Impacted Files	Coverage Δ
pkg/skaffold/plugin/builders/bazel/dependencies.go	93.33% <ø> (ø)
pkg/skaffold/build/local/local.go	33.33% <0%> (ø)
pkg/skaffold/plugin/builders/bazel/builder.go	15% <0%> (ø)
pkg/skaffold/build/local/bazel.go	0% <0%> (ø)
pkg/skaffold/plugin/builders/bazel/bazel.go	0% <0%> (ø)
pkg/skaffold/plugin/builders/bazel/local.go	17.54% <17.54%> (ø)

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[priyawadhwa]

Let's hold off on merging this until the package structure is confirmed --

[priyawadhwa]

CI actually passed (red because of the netlify checks) so I'm gonna go ahead and merge this.