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/zsys_netbsd.go

@@ -0,0 +1,30 @@
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
+// cgo -godefs defs_netbsd.go
+
+package ipv4
+
+const (
+	sysIP_OPTIONS     = 0x1
+	sysIP_HDRINCL     = 0x2
+	sysIP_TOS         = 0x3
+	sysIP_TTL         = 0x4
+	sysIP_RECVOPTS    = 0x5
+	sysIP_RECVRETOPTS = 0x6
+	sysIP_RECVDSTADDR = 0x7
+	sysIP_RETOPTS     = 0x8
+	sysIP_RECVIF      = 0x14
+	sysIP_RECVTTL     = 0x17
+
+	sysIP_MULTICAST_IF    = 0x9
+	sysIP_MULTICAST_TTL   = 0xa
+	sysIP_MULTICAST_LOOP  = 0xb
+	sysIP_ADD_MEMBERSHIP  = 0xc
+	sysIP_DROP_MEMBERSHIP = 0xd
+
+	sizeofIPMreq = 0x8
+)
+
+type ipMreq struct {
+	Multiaddr [4]byte /* in_addr */
+	Interface [4]byte /* in_addr */
+}