skaffold generate-pipeline command

[marlon-gamez]

This pr adds a new skaffold command that allows users to generate a Tekton pipeline (https://github.com/tektoncd/pipeline) by reading their skaffold config file and generating corresponding build and deploy tasks. The command also adds a profile to the users skaffold.yaml, which is used by the pipeline when running the tasks on cluster.

In order to use the generated pipeline, the user must run the command, then commit and push the changes to their skaffold config file.

Currently, building on this branch won't work because the tekton api has outdated dependencies, which has been addressed in this pr (tektoncd/pipeline#1117). Building should be fixed once the next release of Tekton pipelines is out.

TODO:

• add integration tests
• update Tekton dependency when new release occurs

[priyawadhwa]

This is looking really good! Left some organizational comments and nits :)

[tejal29]

@marlon-gamez Can you also run go mod tidy to prune unused dependencies?
I dont' think we are using all of Tekton. Let me know if you don't see the number of files reduced.

[tejal29]

one small nit remaing

INFO [loader] SSA repr building timing: packages building 287.10442ms, total 6.187174947s 
204integration/generate_pipeline_test.go:38:3: U1000: field `args` is unused (unused)
205		args        []string

[codecov]

Codecov Report

Merging #2567 into master will decrease coverage by 0.46%.
The diff coverage is 52.4%.

Impacted Files	Coverage Δ
pkg/skaffold/runner/runner.go	0% <ø> (ø)	⬆️
cmd/skaffold/app/cmd/cmd.go	68% <100%> (+0.25%)	⬆️
pkg/skaffold/pipeline/task.go	100% <100%> (ø)
pkg/skaffold/pipeline/pipeline.go	100% <100%> (ø)
pkg/skaffold/runner/generate_pipeline.go	43.97% <43.97%> (ø)
cmd/skaffold/app/cmd/generate_pipeline.go	45.45% <45.45%> (ø)
pkg/skaffold/pipeline/pipeline_resource.go	68.42% <68.42%> (ø)
... and 2 more

fixed