Use caddy's certmagic library for extensible/robust ACME handling (#14177)

* use certmagic for more extensible/robust ACME cert handling

* accept TOS based on config option

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>

vendor/golang.org/x/net/ipv4/sockopt_stub.go

@@ -0,0 +1,42 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !aix,!darwin,!dragonfly,!freebsd,!linux,!netbsd,!openbsd,!solaris,!windows,!zos
+
+package ipv4
+
+import (
+	"net"
+
+	"golang.org/x/net/bpf"
+	"golang.org/x/net/internal/socket"
+)
+
+func (so *sockOpt) getMulticastInterface(c *socket.Conn) (*net.Interface, error) {
+	return nil, errNotImplemented
+}
+
+func (so *sockOpt) setMulticastInterface(c *socket.Conn, ifi *net.Interface) error {
+	return errNotImplemented
+}
+
+func (so *sockOpt) getICMPFilter(c *socket.Conn) (*ICMPFilter, error) {
+	return nil, errNotImplemented
+}
+
+func (so *sockOpt) setICMPFilter(c *socket.Conn, f *ICMPFilter) error {
+	return errNotImplemented
+}
+
+func (so *sockOpt) setGroup(c *socket.Conn, ifi *net.Interface, grp net.IP) error {
+	return errNotImplemented
+}
+
+func (so *sockOpt) setSourceGroup(c *socket.Conn, ifi *net.Interface, grp, src net.IP) error {
+	return errNotImplemented
+}
+
+func (so *sockOpt) setBPF(c *socket.Conn, f []bpf.RawInstruction) error {
+	return errNotImplemented
+}