Merge tag 'net-next-20250708' of https://source.denx.de/u-boot/custodians/u-boot-net

Pull request net-next-20250708

lwip:
- Call sys_check_timeouts() and schedule() on RX to fix an issue on
  boards with a watchdog and simplify the code
- Enable IP_FRAG and IP_REASSEMBLY
- Add support for setting the TFTP blocksize at runtime
- Fix DNS initialization in wget
- Add the sntp command
- Move code from net/lwip/${cmd}.c to cmd/lwip/${cmd}.c