This PR enables jobs configured with a custom sidecar_task to make
use of the `service.expose` feature for creating checks on services
in the service mesh. Before we would check that sidecar_task had not
been set (indicating that something other than envoy may be in use,
which would not support envoy's expose feature). However Consul has
not added support for anything other than envoy and probably never
will, so having the restriction in place seems like an unnecessary
hindrance. If Consul ever does support something other than Envoy,
they will likely find a way to provide the expose feature anyway.

Fixes #9854