Auto sync with Skaffold

[dgageot]

This is WIP to introduce auto-sync configuration to Buildpacks artifacts.

This feature requires collaboration from the buildpacks that have to export the sync metadata and also that need to be able to build a container image used just for dev.

!!This is very early stage. Many things need to be improved!!

Signed-off-by: David Gageot david@gageot.net

[loosebazooka]

@dgageot I think there might be some conflicts between this and #3382. Also, I'm curious about autosync being on by default (for jib at least).

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@ae6f5ce). Click here to learn what that means.
The diff coverage is 18.75%.

Impacted Files	Coverage Δ
pkg/skaffold/build/local/local.go	60% <0%> (ø)
pkg/skaffold/docker/image_util.go	0% <0%> (ø)
pkg/skaffold/build/buildpacks/lifecycle.go	63.46% <0%> (ø)
pkg/skaffold/build/buildpacks/metadata.go	11.11% <0%> (ø)
pkg/skaffold/sync/sync.go	65.82% <0%> (ø)
pkg/skaffold/build/cache/lookup.go	100% <100%> (ø)
pkg/skaffold/build/buildpacks/types.go	100% <100%> (ø)
pkg/skaffold/build/cache/hash.go	75.94% <100%> (ø)
pkg/skaffold/build/local/types.go	69.44% <100%> (ø)
pkg/skaffold/build/cache/cache.go	56.81% <100%> (ø)
... and 1 more