Support for multiple swagger input (multiple clients in one package)

[xirzec]

Commonly services will describe their API surface using multiple swagger files, but we often wish to still ship this out of one JS package.

Minimal work here would be to figure out a way to have the generator run multiple times and export both clients from a root folder (we do this manually in convenience clients today)

[sarangan12]

monitor SDK is one of the examples for this scenario