E2E Test workflow should reuse the result of Build and Test

[squizzi]

Currently the E2E tests workflow builds and pushes it's own tag to the charts ci repo, however it would be better if the Build and Test workflow conducted the docker-build and pushed it to the CI repo only after unit testing was complete and then the E2E test repo reused the result of this build instead of conducting it again.

In order for this to happen we'll need to make the E2E tests repo either reuse the Build and Test workflow OR just make it depend on that running and move the pushing step into Build and Test, the tricky part is figuring out how to continue to support a labeled pull_request event with type workflow_run