* api: add support for SocketAddress types in ManagedChannelProvider
also add support for SocketAddress types in NameResolverProvider
Use scheme in target URI to select a NameRseolverProvider and get
that provider's supported SocketAddress types.
implement selection in ManagedChannelRegistry of appropriate
ManagedChannelProvider based on NameResolver's SocketAddress types
sanjaypujare
DNVindhya