This is a work-in-progress changeset to provide workload-specific Consul tokens
that are created by the `consul_hook` and attached to workload registration
requests by the `group_service_hook` and `service_hook`.
This requires unreleased updates to Consul's `api` package, so this changeset
includes a temporary `replace` directive in the go.mod file.
This commit performs refactoring to pull out common service
registration objects into a new `client/serviceregistration`
package. This new package will form the base point for all
client specific service registration functionality.
The Consul specific implementation is not moved as it also
includes non-service registration implementations; this reduces
the blast radius of the changes as well.
