Add E2E tests to run on deployment

[jsdw]

Soemthing that would be nice to have is a set of end to end tests that automatically run against the deployed instacne of telemetry, and mark the deployment as failed if they don't succeed.

Helm has a means to do this (see https://helm.sh/docs/topics/chart_tests/), and there currently exist some E2E tests under backend/telemetry_core/tests.

If we thought it valuable enough, we could:

• Re-package the (or some of the) E2E tests into a separate e2e binary which can be given the relevant URLs and run tests against them. Currently, some tests can run against external URLs and some tests will fail as they want to control thecreation and deletion of shards and such. This binary could mark each test as being "local" or "any" (or something like that) so that it can run a full suite by locally spinning up binaries (as happens at present) or run only a subset of the tests which are happy with a pre-existing deployment.
• Add a helm test which kicks off an image to run the above e2e binary against the deployed telemetry instance.