Support forwarded arguments in calls, super, and nested blocks

[pvcresin]

Known issue: forwarding-arguments

Summary

• support argument forwarding with ... in direct calls, super(...), and nested blocks
• move the forwarding-arguments case from known issues to regular scenarios
• add scenario coverage for bar(...), super(...), and 1.times { bar(...) }

Design

• model ... as forwarded actual arguments instead of reconstructing it from local variables
• keep the forwarding state in a dedicated object referenced from LocalEnv
• reuse the same forwarding state for super(...) and nested block bodies

Note

The implementation is based on the existing argument-binding logic in MethodDefBox#pass_arguments.

ForwardingArguments#accept_actual_arguments mirrors that flow to capture the actual arguments received by def foo(...), and ForwardingArguments#to_actual_arguments converts that captured state back into ActualArguments for direct calls, super(...), and nested block calls.