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/insomniacslk/dhcp/dhcpv4/option_string.go

@@ -0,0 +1,84 @@
+package dhcpv4
+
+// String represents an option encapsulating a string in IPv4 DHCP.
+//
+// This representation is shared by multiple options specified by RFC 2132,
+// Sections 3.14, 3.16, 3.17, 3.19, and 3.20.
+type String string
+
+// ToBytes returns a serialized stream of bytes for this option.
+func (o String) ToBytes() []byte {
+	return []byte(o)
+}
+
+// String returns a human-readable string.
+func (o String) String() string {
+	return string(o)
+}
+
+// FromBytes parses a serialized stream of bytes into o.
+func (o *String) FromBytes(data []byte) error {
+	*o = String(string(data))
+	return nil
+}
+
+// GetString parses an RFC 2132 string from o[code].
+func GetString(code OptionCode, o Options) string {
+	v := o.Get(code)
+	if v == nil {
+		return ""
+	}
+	return string(v)
+}
+
+// OptDomainName returns a new DHCPv4 Domain Name option.
+//
+// The Domain Name option is described by RFC 2132, Section 3.17.
+func OptDomainName(name string) Option {
+	return Option{Code: OptionDomainName, Value: String(name)}
+}
+
+// OptHostName returns a new DHCPv4 Host Name option.
+//
+// The Host Name option is described by RFC 2132, Section 3.14.
+func OptHostName(name string) Option {
+	return Option{Code: OptionHostName, Value: String(name)}
+}
+
+// OptRootPath returns a new DHCPv4 Root Path option.
+//
+// The Root Path option is described by RFC 2132, Section 3.19.
+func OptRootPath(name string) Option {
+	return Option{Code: OptionRootPath, Value: String(name)}
+}
+
+// OptBootFileName returns a new DHCPv4 Boot File Name option.
+//
+// The Bootfile Name option is described by RFC 2132, Section 9.5.
+func OptBootFileName(name string) Option {
+	return Option{Code: OptionBootfileName, Value: String(name)}
+}
+
+// OptTFTPServerName returns a new DHCPv4 TFTP Server Name option.
+//
+// The TFTP Server Name option is described by RFC 2132, Section 9.4.
+func OptTFTPServerName(name string) Option {
+	return Option{Code: OptionTFTPServerName, Value: String(name)}
+}
+
+// OptClassIdentifier returns a new DHCPv4 Class Identifier option.
+//
+// The Vendor Class Identifier option is described by RFC 2132, Section 9.13.
+func OptClassIdentifier(name string) Option {
+	return Option{Code: OptionClassIdentifier, Value: String(name)}
+}
+
+// OptUserClass returns a new DHCPv4 User Class option.
+func OptUserClass(name string) Option {
+	return Option{Code: OptionUserClassInformation, Value: String(name)}
+}
+
+// OptMessage returns a new DHCPv4 (Error) Message option.
+func OptMessage(msg string) Option {
+	return Option{Code: OptionMessage, Value: String(msg)}
+}