Adds session hosts to an existing host pool. The new hosts are built from the VM settings already saved
on that pool, so those settings must be in place before this call and are not accepted in the request body.

For Entra hosts, provisioning reads the current Azure host-pool RDP properties and adds
enablerdsaadauth:i:1 only if its name is absent. Other properties and explicit values are preserved;
an explicit disabled value produces a warning and does not stop provisioning.
If the RDP properties cannot be read or updated, the job logs a warning and provisioning continues.
This affects pool-wide client connections without changing existing VMs. Clients may need to refresh
their resources to receive the change. Tenant, client, and user-access prerequisites for Entra SSO still apply.
Non-Entra provisioning leaves the pool's RDP properties unchanged.

For pools with a DynamicHosts scaling profile, scale-in cleanup treats all stopped
zero-session hosts above MinHosts as elastic capacity, including manually added hosts.