Ability to share global services with all partitions automatically

When utilizing admin partitions, you can export services and import them to different partitions. But when you have hundreds or thousands of partitions this can become painful to manage and organize.

It would be nice if we could create "global" services in the default partition which then automatically cascade to all other partitions. Examples of this would be DNS, or Vault.

Expanding on this example.
If we have Consul Enterprise partitions a, b and c
and we have Vault Namespaces a, b and c

We don't want to register vault multiple times because that counts against service instances. We also don't want to to configure vault to exported + imported N times as we scale. So we just set vault to global and it shows up in all the consul partitions

This is somewhat related to https://github.com/hashicorp/consul/issues/16189 but ties to any service, not just the consul service

No files, tests, or entry points are named. Start by reviewing related issue #16189 and the existing admin-partition service export/import behavior. Define how a global service in the default partition should cascade to every partition, including the Consul and Vault examples, and how this behaves at large partition counts.

Written by the indexing model from the issue text.