Check multiple settings per update of event loop

It seems that in Qt5, the update loop was triggered a lot more often than in qt6.
Since we used that to handle the error checking, this made it so that you sometimes had to wait
for quite some time untill the slicing would start (as that is blocked by the error checker)

cura/Machines/MachineErrorChecker.py

@@ -53,6 +53,8 @@ class MachineErrorChecker(QObject):
 
         self._keys_to_check = set()  # type: Set[str]
 
+        self._num_keys_to_check_per_update = 10
+
     def initialize(self) -> None:
         self._error_check_timer.timeout.connect(self._rescheduleCheck)
 
@@ -162,6 +164,7 @@ class MachineErrorChecker(QObject):
 
         self._check_in_progress = True
 
+        for i in range(self._num_keys_to_check_per_update):
             # If there is nothing to check any more, it means there is no error.
             if not self._stacks_and_keys_to_check:
                 # Finish
@@ -173,8 +176,7 @@ class MachineErrorChecker(QObject):
 
             enabled = stack.getProperty(key, "enabled")
             if not enabled:
-            self._application.callLater(self._checkStack)
-            return
+                continue
 
             validation_state = stack.getProperty(key, "validationState")
             if validation_state is None:
@@ -192,7 +194,7 @@ class MachineErrorChecker(QObject):
                 keys_to_recheck = {setting_key for stack, setting_key in self._stacks_and_keys_to_check}
                 keys_to_recheck.add(key)
                 self._setResult(True, keys_to_recheck = keys_to_recheck)
-            return
+                continue
 
         # Schedule the check for the next key
         self._application.callLater(self._checkStack)