Use scudo_ring_buffer_size from process_info

This is a no-op but will be used in upcoming scudo changes that allow to
change the buffer size at process startup time, and as such we will no
longer be able to call __scudo_get_ring_buffer_size in debuggerd.

Bug: 263287052
Change-Id: I350421d1fcdf22ce3b8b73780b88c1e10fa8a074