Add host time platform; remove host support from sntp. (#6854)

esphome/components/host/time/host_time.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/components/time/real_time_clock.h"
+
+namespace esphome {
+namespace host {
+
+class HostTime : public time::RealTimeClock {
+ public:
+  void update() override {}
+};
+
+}  // namespace host
+}  // namespace esphome