This has the biggest impact on enterprise test cases that use namespaced
registrations, which prior to this change sometimes failed the initial
registration because the namespace was not yet created.
* Allow setting the mesh gateway mode for an upstream in config files
* Add envoy integration test for mesh gateways
This necessitated many supporting changes in most of the other test cases.
Add remote mode mesh gateways integration test
Additionally:
- wait for bootstrap config entries to be applied
- run the verify container in the host's PID namespace so we can kill
envoys without mounting the docker socket
* assert that we actually send HEALTHY and UNHEALTHY endpoints down in EDS during failover
