selftests/bpf: Expand getsockname and getpeername tests

This expands coverage for getsockname and getpeername hooks to include
getsockname4, getsockname6, getpeername4, and getpeername6.

Signed-off-by: Jordan Rife <jrife@google.com>
Link: https://lore.kernel.org/r/20240510190246.3247730-17-jrife@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>