Initialize SoftAP DhcpServer object on demand (#8546)

* Initialize SoftAP DhcpServer object on demand

Remove dependency on global ctor, and just construct the object when
someone asks us to do it. Only dependency right now is netif_git, which
is expected to be initialized by the lwip code some time before
dhcps_start happens.

Removing ip_info from begin(), since we never reference later on.
Also removing the specific check for netif id and simplify the ctors.

Update tests and recover old nonos-sdk dhcps functions that were not implemented.

* nonos helpers have a separate header

* wifi ap needs this anyway, simplify sketch includes

* missing example

* existing name :/

* trying to fix header dependency

* restyle

* not a c header

* no need to init

* move dhcp server getter to WiFi

more... arduino'ish? we ahve object as namespace, plus everything else
related to softAP is there
redundant includes, redundant mock impl (out-of-scope here to fix)

* ...move things back, still expose as WiFi method

* review fix

* include -nonos header in wifi lib though

* no more lwip include

* style

* need mock dhcpserver instance

tests/host/common/DhcpServer.cpp

@@ -0,0 +1,80 @@
+#include <LwipDhcpServer.h>
+#include <LwipDhcpServer-NonOS.h>
+
+DhcpServer& getNonOSDhcpServer()
+{
+    static DhcpServer instance(nullptr);
+    return instance;
+}
+
+bool DhcpServer::set_dhcps_lease(struct dhcps_lease* please)
+{
+    (void)please;
+    return false;
+}
+
+bool DhcpServer::set_dhcps_lease_time(uint32 minute)
+{
+    (void)minute;
+    return false;
+}
+
+bool DhcpServer::set_dhcps_offer_option(uint8 level, void* optarg)
+{
+    (void)level;
+    (void)optarg;
+    return false;
+}
+
+void DhcpServer::end() { }
+
+bool DhcpServer::begin()
+{
+    return false;
+}
+
+DhcpServer::DhcpServer(netif*) { }
+
+DhcpServer::~DhcpServer()
+{
+    end();
+}
+
+extern "C"
+{
+#include <user_interface.h>
+
+    bool wifi_softap_dhcps_start(void)
+    {
+        return true;
+    }
+
+    enum dhcp_status wifi_softap_dhcps_status(void)
+    {
+        return DHCP_STARTED;
+    }
+
+    bool wifi_softap_dhcps_stop(void)
+    {
+        return true;
+    }
+
+    bool wifi_softap_set_dhcps_lease(struct dhcps_lease* please)
+    {
+        (void)please;
+        return true;
+    }
+
+    bool wifi_softap_set_dhcps_lease_time(uint32 minute)
+    {
+        (void)minute;
+        return true;
+    }
+
+    bool wifi_softap_set_dhcps_offer_option(uint8 level, void* optarg)
+    {
+        (void)level;
+        (void)optarg;
+        return true;
+    }
+}