Make broadcast constraints variadic

[manopapad]

E.g., it would be nicer to write:

broadcast("x", "y", "z", ("w", 0), ("u", 1, 2))

Instead of:

broadcast("x"), broadcast("y"), broadcast("z"), broadcast("w", (0,)), broadcast("u", (1, 2))

It's just ugly and makes it harder to read, especially when you have to constrain a bunch of parameters at once.

[elliottslaughter]

This would be useful for the SLAC/LANL project.

[Jacobfaib]

Same with align() too I guess? Any others?

[elliottslaughter]

Yes, please do align as well.

I looked at the others a while back, and I didn't see any others where it would obviously make sense to do this, and for my personal use case I don't need them. But maybe someone else has a different opinion.