[Feature #17045] ObjectSpace.dump_all should allocate as little as possible in the GC heap
Up until this commit ObjectSpace.dump_all allocates two Hash because of `rb_scan_args`.
It also can allocate a `File` because of `rb_io_get_write_io`.
These allocations are problematic because `dump_all` dumps the Ruby
heap, so it should try modify as little as possible what it is
observing.