Support forwarded arguments in calls and super

[pvcresin]

Known issue: forwarding-arguments

Summary

• support Ruby argument forwarding with ...
• forward arguments through method calls, super, and nested blocks

## update
def foo(...)
  1.times { bar(...) }
end

def bar(*a, **b)
  [a, b]
end

foo(1, x: 4, y: 5)

## assert
class Object
  def foo: (*Integer, **Integer) -> Integer
  def bar: (*Integer, **Integer) -> [Array[Integer], { x: Integer, y: Integer }]
end

Design

• treat ... as forwarded actual arguments
• avoid spreading forwarding-specific state across LocalEnv
• keep anonymous block forwarding (&) separate from ...

[pvcresin]

I think I need a little more time to refine the strategy, so I’ll close this for now.