Matter requires that regular Matter messages fit in IPv6 MTU
of 1280 bytes so the default packet buffer size of 1583 bytes
seems excessively large for some configurations. Especially
that the buffers only hold the UDP payload in the case of
non-LWIP transports.

There are two exceptions to the above though:
1. Minimal mDNS uses the same packet buffer pool and mDNS
   message size is not limited to 1280 bytes, so shrinking
   the buffer size below MTU might have a negative impact
   on the mDNS behavior.
2. Matter allows definining so called large messages that
   can be bigger than 1280 bytes and sent over TCP, but that
   is not implemented yet and will likely require a different
   allocation mechanism.

Signed-off-by: Damian Krolik <[email protected]>

…transmissions (#33334)

On constrained devices, the number of available packet
buffers can be very low. During stress testing a device
that has 8 buffers available, which is the default on
many platforms, it was observed that the device would
receive a lot of parallel read requests and then it
would use all its buffers for responses. The responses
would then be stored in the retransmission table,
awaiting an ACK, but the ACK would never arrive because
of lack of available buffers.

Configure the retransmission table size to be less than
the number of packet buffers to make sure that not all
buffers are held by the retransmission entries, in which
case the device is unable to receive an ACK and hence it
becomes unavailable until any message times out.

Signed-off-by: Damian Krolik <[email protected]>