E2E Workflow Scripts: Use cyberark/demo-app directly from DockerHub instead of building a custom image

[imheresamir]

Describe the solution you would like

E2E workflow scripts should not need to build a custom cyberark/demo-app PetStore sample app to include the summon binaries. See the linked issue below in which summon was added to the demo-app. This is the tracking issue for removing the custom image building and just using the cyberark/demo-app image from DockerHub after it has been updated.

Additional context

I think we should rip all this out in favour of having summon in the demo app (see conjurdemos/pet-store-demo#35).

Originally posted by @doodlesbykumbi in #307 (comment)

[jtuttle]

The demo-app image has not been pushed to DockerHub for a year and a half, we may need to do a tagged release to get a newer version pushed.