JDK-8224815 changed the underlying data for CompressedOops, eliminating _narrow_ptrs_base and instead using only _narrow_oop, updating the functions ptrs_base() and ptrs_base_addr() accordingly. However, this made ptrs_base() identical to base(). Rather than two functions that do the same thing, ptrs_base() should be removed and callers should use base(). That leaves ptrs_base_addr() orphaned and misnamed, so rename it to base_addr().