Current infra.proto is too rigid

[ajbalogh]

The current infra.proto is too rigid and has introduced structured messages to describe Infrastructure.

The intent of infra.proto is to have a set of messages to express infrastructure as a graph, not to introduce rigid high level concepts such as clos fabric, a single set of hosts etc. Those concepts should be provided by a higher level of application messages and/or helper code which should ultimately populate the base infra.proto messages.

To reiterate, infra.proto is strictly meant to capture infrastructure as a graph.