Fix lint issues with golangci-lint@v2

Add a quota handler callback

This PR adds a quota handler callback function which, if specified, is
called by the server just before making an allocation for a user. The
handler should return a single bool: if true then the allocation
request can proceed, otherwise the request is rejected with a 486
(Allocation Quota Reached) error.

Lower priority of per-packet error message

The error message "Failed to handle datagram" is generated for
each received packet; it can therefore be used by an attacker to
fill the server's logs by sending a burst of incorrect packets.

Lower its priority to debug.

Avoid calling String() on nil turn address

Update module github.com/pion/stun/v3 to v3.0.0

Prevent heap allocations in FiveTuple Fingerprint

Prevent heap allocations in FiveTuple Fingerprint

Support stand alone STUN server mode

Running in stand alone STUN server does not start
due to packet conn config requiring relay address config
during validation.

To enable that mode, bypass validation if relay address config
in packet conn config is nil.

Note that it is still validated in `ListenerConfig`.

Use signed timestamp for nonce

Fix out of bounds access panic

Drop packet exceeding size of input buffer.