homing: Create QueryEndstops class from gcode

Create the QueryEndstops in the gcode handler instead of in the
kinematic classes.  This simplifies the gcode handler as it can
directly register its response callback.

Also, store the stepper name in the stepper class.  Also, propagate
the print_time of the query request to the mcu_endstop class.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/mcu.py

@@ -140,10 +140,11 @@ class MCU_endstop:
         if self._stepper.get_invert_dir():
             return -pos
         return pos
-    def query_endstop(self):
+    def query_endstop(self, mcu_time):
+        clock = int(mcu_time * self._mcu_freq)
         self._homing = False
         self._min_query_time = time.time()
-        self._next_query_clock = 0
+        self._next_query_clock = clock
     def get_last_triggered(self):
         return self._last_state.get('pin', self._invert) ^ self._invert