This flag is set when the caller has already created a new array to handle a splat, such as for `f(*a, b)` and `f(*a, *b)`. Previously, if `f` was defined as `def f(*a)`, these calls would create an extra array on the callee side, instead of using the new array created by the caller. This modifies `setup_args_core` to set the flag whenver it would add a `splatarray true` instruction. However, when `splatarray true` is changed to `splatarray false` in the peephole optimizer, to avoid unnecessary allocations on the caller side, the flag must be removed. Add `optimize_args_splat_no_copy` and have the peephole optimizer call that. This significantly simplifies the related peephole optimizer code. On the callee side, in `setup_parameters_complex`, set `args->rest_dupped` to true if the flag is set. This takes a similar approach for optimizing regular splats that was previiously used for keyword splats in d2c41b1bff1f3102544bb0d03d4e82356d034d33 (via VM_CALL_KW_SPLAT_MUT).