Major refactor

Add P1 tests to integration and validation

Falling back to default ~/.kube/config if no KUBECONFIG env is set for client-go

This is the default rio behavior, we should do the same

Removing unused python dependencies from CI Dockerfile

Adding validations to scale tests

This is part of #559 Add kubectl validations to the test framework

Reordering the validations in CI

Add route test and kubectl validations

Adding extra validations using kubectl for service endpoints

This validates the endpoint URLs generated by rio for the revisions and Global are present.
- Making improvements based on PR feedback
- Getting the url hostname only to compare the endpoint between kubectl and rio

Add roundtrip stack export integration test

Add wrapper for kubectl

Use k8s wait method and scale wait times to remove flakiness

Fix bug to allow riofile export to have multiples

Also add stack to rm types in CLI

Bump serving max-scale-up-rate to allow scaling

Automation scale and run tests

- Porting run tests from python to go spec.
- Adding scale up to 3, 5 and 10 scale tests.
- Removing python CI scripts from executing.

Add ability to provide imagePath in Riofile

Move to go testing

Currently this acts as a max rate, rather than max over tick-interval.
Bringing this inline with the upstream changes:
https://github.com/knative/serving/pull/4527/commits/4b0c4ffd0ff0bf6b2a5912960ca4c8c0ed2902ec

Use of kubectl instead of an alias

fix typo

In order to onboard devs and the community faster we are unifying
the codebase into go. We are also moving towards BDD style specs so
that the tests are more human readable, and our current suite (and its
gaps) are more immediately obvious.

Update README with slack info

Update readme for slack info

README update: route insert is a flag on add, not standalone