Merge bitcoin/bitcoin#34346: test: use IP_PORTRANGE_HIGH on FreeBSD for dynamic port allocation

2845f10a2b test: extend FreeBSD ephemeral port range fix to P2P listeners (node)
34bed0ed8c test: use IP_PORTRANGE_HIGH on FreeBSD for dynamic port allocation (woltx)

Pull request description:

  Reopening #34336. I’ve now tested it on FreeBSD and confirmed it works.

  On FreeBSD, the default ephemeral port range (10000-65535) overlaps with the test framework's static port range (11000-26000), possibly causing intermittent "address already in use" failures when tests use dynamic port allocation (`port=0`).

  This PR adds a helper that sets `IP_PORTRANGE_HIGH` via `setsockopt()` before binding, requesting ports from 49152-65535 instead, which avoids the overlap, as suggested in https://github.com/bitcoin/bitcoin/issues/34331#issuecomment-3767161843 by @maflcko .

  From FreeBSD's [sys/netinet/in.h](https://cgit.freebsd.org/src/tree/sys/netinet/in.h):
    ```c
    #define IP_PORTRANGE         19
    #define IP_PORTRANGE_HIGH    1
    #define IPPORT_EPHEMERALFIRST 10000  /* default range start */
    #define IPPORT_HIFIRSTAUTO   49152   /* high range start */
  ```

  See also: FreeBSD https://man.freebsd.org/cgi/man.cgi?query=ip&sektion=4 man page.

  Fixes #34331

ACKs for top commit:
  vasild:
    ACK 2845f10a2b
  hebasto:
    ACK 2845f10a2b, I have reviewed the code and it looks OK.

Tree-SHA512: ce501ce3e8a4023e07bad572df2b85d6829becf133813e4529aebba83e4eba59fa8b48e9d2197ebbb226adaf3054fad720775a787244d6b38c0078ee086102f4

test/functional/test_framework/p2p.py

@@ -22,9 +22,11 @@ P2PTxInvStore: A p2p interface class that inherits from P2PDataStore, and keeps
 
 import asyncio
 from collections import defaultdict
+import ipaddress
 from io import BytesIO
 import logging
 import platform
+import socket
 import struct
 import sys
 import threading
@@ -76,6 +78,9 @@ from test_framework.messages import (
     MAGIC_BYTES,
     sha256,
 )
+from test_framework.netutil import (
+    set_ephemeral_port_range,
+)
 from test_framework.util import (
     assert_not_equal,
     MAX_NODES,
@@ -793,8 +798,22 @@ class NetworkThread(threading.Thread):
             # connections, we can accomplish this by providing different
             # `proto` functions
 
-            listener = await cls.network_event_loop.create_server(peer_protocol, addr, port)
-            port = listener.sockets[0].getsockname()[1]
+            if port == 0:
+                # Manually create the socket in order to set the range to be
+                # used for the port before the bind() call.
+                if ipaddress.ip_address(addr).version == 4:
+                    address_family = socket.AF_INET
+                else:
+                    address_family = socket.AF_INET6
+                s = socket.socket(address_family)
+                set_ephemeral_port_range(s)
+                s.bind((addr, 0))
+                s.listen()
+                listener = await cls.network_event_loop.create_server(peer_protocol, sock=s)
+                port = listener.sockets[0].getsockname()[1]
+            else:
+                listener = await cls.network_event_loop.create_server(peer_protocol, addr, port)
+
             logger.debug("Listening server on %s:%d should be started" % (addr, port))
             cls.listeners[(addr, port)] = listener