[FIRRTL] Don't allow foreign types in wires or connects.

[darthscsi]

This forces dialects to handle storing their own types in their own ops and not tie them to firrtl connect semantics. To make this a bit easier, a new connect-like operation exists only for setting the value of foreign-typed output ports and instance inputs.

With this, foreign types may appear ONLY as module port types and will not appear in any (except foreign_output) firrtl operation or type.

There's a fair amount of simplification this will allow in the various passes' logic.

[darthscsi]

More tests comming.

[darthscsi]

@prithayan How breaking to you is this?

[prithayan]

@prithayan How breaking to you is this?

Wire and connect is primarily being used with libdn.channel<> types, the wire serves a temporary, to use a value that is defined later . I can start working on eliminating their usage. Need to investigate a bit more on the ports usage.