Run e2e tests on bare-metal Buildkite agents on every commit to master (non-blocking)

Created by: slimsag

Every commit to master should run e2e tests on the bare-metal buildkite agents once https://github.com/sourcegraph/sourcegraph/issues/12101 is closed.

It should not block the build at all (adds no time to CI runs, and if it fails should not show the build as failed).