move netdev and netlink into their own packages and out of drivers

This moves the netdev/netlink namespace out of drivers and into their
own packages.  Also, defines netdev and netlink as L3/L4 and L2 OSI
layers, respectively.  Move some L3 functionality from netlink to
netdev (GetIPAddr).

For netlink, add ConnectParams for NetConnect to pass in L2 connection
parameters (ssid, pass, auth_type, etc).  Also adds connection mode
(STA, AP, etc).

For netlink, add SendEth and RecvEthFunc funcs to handle L2 send/recv of
Ethernet pkts.

examples/net/http-get/main.go

@@ -9,6 +9,8 @@
 //     examples/net/webclient (for HTTP)
 //     examples/net/tlsclient (for HTTPS)
 
+//go:build pyportal || nano_rp2040 || metro_m4_airlift || arduino_mkrwifi1010 || matrixportal_m4 || wioterminal
+
 package main
 
 import (
@@ -20,6 +22,9 @@ import (
 	"net/url"
 	"strings"
 	"time"
+
+	"tinygo.org/x/drivers/netlink"
+	"tinygo.org/x/drivers/netlink/probe"
 )
 
 var (
@@ -31,7 +36,13 @@ func main() {
 
 	waitSerial()
 
-	if err := netdev.NetConnect(); err != nil {
+	link, _ := probe.Probe()
+
+	err := link.NetConnect(&netlink.ConnectParams{
+		Ssid:       ssid,
+		Passphrase: pass,
+	})
+	if err != nil {
 		log.Fatal(err)
 	}