Require metadata on all topology

[henryh2]

Requires metadata to be set on all topology, including both tree and block topology.

[henryh2]

Two comments regarding this PR, the first of which is:

If the topology request payload specifies a topology plugin (either tree or block) that is different than the topology that can be provided, what should be the action? Return an error in the request?

[henryh2]

And second, for MNNVL, is block topology always returned (current implementation), or should tree topology be returned in some situations?

[dmitsh]

If the topology request payload specifies a topology plugin (either tree or block) that is different than the topology that can be provided, what should be the action? Return an error in the request?

Toposim (and GTS) returns a collections of nodes with their local topology (a chain of switches and/or presence of nvlink).
From here we can construct either tree or block topology. So, IIUC, it is up to the requester to define. IMO we should consider tree topology as default.