Allow vector input to functions taking vectors

[kcrisman]

That is really vague. What I mean is what is described at ​this ask.sagemath.org request.

var('x,y,z,t')

g(t) = (t, t^2, t^3)

f(x,y,z) = (2x,y+x+z,yx)

wants to have f(g(t)) 'just work', though one poster points out that f(*g(t)) does.

We'd want this to work for explicit vector objects, too.

[kcrisman]

#11507 is related, but separate.