net.IPFromString misparses ::ffff:0.0.0.0

[taktv6]

Describe the bug
When parsing ::ffff:0.0.0.0 net.IPFromString returns an all zero IPv4 address while IPv6 is expected.

Steps to Reproduce

import (
	"fmt"
	"net"

	bnet "github.com/bio-routing/bio-rd/net"
)

func main() {
	bio()
	upstream()
}

func upstream() {
	fmt.Printf("golang net:\n")
	ip := net.ParseIP("::ffff:0.0.0.0")
	v4 := ip.To4()
	if v4 != nil {
		fmt.Printf("is IPv4!\n")
	}

	v6 := ip.To16()
	if v6 != nil {
		fmt.Printf("Is IPv6!\n")
	}

	fmt.Printf("v4: %s\n", v4.String())
	fmt.Printf("v6: %s\n", v6.String())
}

func bio() {
	fmt.Printf("bio net:\n")
	ip, err := bnet.IPFromString("::ffff:0.0.0.0")
	if err != nil {
		panic(err)
	}

	fmt.Printf("Is IPv4: %v\n", ip.IsIPv4())

	fmt.Printf("Addr: %s\n", ip.String())
}

Is IPv4: true
Addr: 0.0.0.0
golang net:
is IPv4!
Is IPv6!
v4: 0.0.0.0
v6: 0.0.0.0```
**Expected behavior**
net.IPFromString should return `::ffff:0.0.0.0` or `::ffff:0:0`

**Additional context**
This behavior was inherited from upstream net.ParseIP function. It basically casts any IPv6 mapped IPv4 address into a pure IPv4 address from which it is not possible to detect that it actually was an IPv6 address.