Add a test for minimum receive buffer size used in setsockopt.
Add a test for minimum receive buffer size used in setsockopt.

In Linux, the minimum buffer size used in setsockopt for SO_SNDBUF and
SO_RCVBUF option is the value defined in SOCK_MIN_RCVBUF and SOCK_MIN_SNDBUF.
(These values depend on the struct sk_buff size).

The minimum buffer size for SO_RCVBUF in gVisor is 4KiB. Since the value in
Linux is based on sk_buff size, it is not useful to have the same limits set
in gVisor. Added a syscall test to verify the minimum receive buffer size.

PiperOrigin-RevId: 421642931

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor