fix(dhcp): can not renew an ip address

The dhcp server is systemd-networkd, and the dhcp
plugin can request an ip but can not renew it.
The systemd-networkd just ignore the renew request.

```
2024/09/14 21:46:00 no DHCP packet received within 10s
2024/09/14 21:46:00 retrying in 31.529038 seconds
2024/09/14 21:46:42 no DHCP packet received within 10s
2024/09/14 21:46:42 retrying in 63.150490 seconds
2024/09/14 21:47:45 98184616c91f15419f5cacd012697f85afaa2daeb5d3233e28b0ec21589fb45a/iot/eth1: no more tries
2024/09/14 21:47:45 98184616c91f15419f5cacd012697f85afaa2daeb5d3233e28b0ec21589fb45a/iot/eth1: renewal time expired, rebinding
2024/09/14 21:47:45 Link "eth1" down. Attempting to set up
2024/09/14 21:47:45 98184616c91f15419f5cacd012697f85afaa2daeb5d3233e28b0ec21589fb45a/iot/eth1: lease rebound, expiration is 2024-09-14 22:47:45.309270751 +0800 CST m=+11730.048516519
```

Follow the https://datatracker.ietf.org/doc/html/rfc2131#section-4.3.6,
following options must not be sent in renew

- Requested IP Address
- Server Identifier

Since the upstream code has been inactive for 6 years,
we should switch to another dhcpv4 library.
The new selected one is https://github.com/insomniacslk/dhcp.

Signed-off-by: Songmin Li <lisongmin@protonmail.com>

vendor/github.com/u-root/uio/rand/random_linux.go

@@ -0,0 +1,77 @@
+// Copyright 2019 the u-root Authors. All rights reserved
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package rand
+
+import (
+	"context"
+	"log"
+	"os"
+	"sync"
+	"syscall"
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+var defaultContextReader = &getrandomReader{}
+
+var backupReader = &urandomReader{}
+
+type getrandomReader struct {
+	once   sync.Once
+	backup bool
+}
+
+// ReadContext implements a cancelable read from /dev/urandom.
+func (r *getrandomReader) ReadContext(ctx context.Context, b []byte) (int, error) {
+	r.once.Do(func() {
+		if os.Getenv("UROOT_NOHWRNG") != "" {
+			r.backup = true
+			return
+		}
+		if _, err := unix.Getrandom(b, unix.GRND_NONBLOCK); err == syscall.ENOSYS {
+			r.backup = true
+		}
+	})
+	if r.backup {
+		return backupReader.ReadContext(ctx, b)
+	}
+
+	for {
+		// getrandom(2) with GRND_NONBLOCK uses the urandom number
+		// source, but only returns numbers if the crng has been
+		// initialized.
+		//
+		// This is preferrable to /dev/urandom, as /dev/urandom will
+		// make up fake random numbers until the crng has been
+		// initialized.
+		n, err := unix.Getrandom(b, unix.GRND_NONBLOCK)
+		if err == nil {
+			return n, nil
+		}
+		select {
+		case <-ctx.Done():
+			return 0, ctx.Err()
+
+		default:
+			if err != syscall.EAGAIN && err != syscall.EINTR {
+				return n, err
+			}
+		}
+	}
+}
+
+// ReadContextWithSlowLogs logs a helpful message if it takes a significant
+// amount of time (>2s) to produce random data.
+func (r *getrandomReader) ReadContextWithSlowLogs(ctx context.Context, b []byte) (int, error) {
+	d := 2 * time.Second
+	t := time.AfterFunc(d, func() {
+		log.Printf("getrandom is taking a long time (>%v). "+
+			"If running on hardware, consider enabling Linux's CONFIG_RANDOM_TRUST_CPU=y. "+
+			"If running in a VM/emulator, try setting up virtio-rng.", d)
+	})
+	defer t.Stop()
+	return r.ReadContext(ctx, b)
+}