Undocument and deprecate redundant sprite group classes

To clean up the sprite documentation I've removed three classes that do nothing. I've also removed OrderedUpdates from the code, it became effectively redundant after we dropped Python 3.5 support and all dictionaries became ordered. Ordered dictionaries were then made part of the Python specification in version 3.7 which is currently our lowest supported version.

Author: MyreMylar

docs/reST/ref/sprite.rst

@@ -203,7 +203,8 @@ Sprites are not thread safe. So lock them yourself if using threads.
 
    A simple container for Sprite objects. This class can be inherited to create
    containers with more specific behaviors. The constructor takes any number of
-   Sprite arguments to add to the Group. The group supports the following
+   Sprite arguments to add to the Group. All sprites in groups are stored in the
+   order they were added to the group. The group supports the following
    standard Python operations:
 
    ::
@@ -297,8 +298,7 @@ Sprites are not thread safe. So lock them yourself if using threads.
       ``Sprite.image`` attribute for the source surface, and ``Sprite.rect``
       for the position.
 
-      The Group does not keep sprites in any order, so the draw order is
-      arbitrary.
+      The Group keeps sprites in the order they were added, they will be drawn in this order.
 
       .. ## Group.draw ##
 
@@ -337,22 +337,6 @@ Sprites are not thread safe. So lock them yourself if using threads.
 
    .. ## pygame.sprite.Group ##
 
-.. class:: RenderPlain
-
-   | :sl:`Same as pygame.sprite.Group`
-
-   This class is an alias to ``pygame.sprite.Group()``. It has no additional functionality.
-
-   .. ## pygame.sprite.RenderClear ##
-
-.. class:: RenderClear
-
-   | :sl:`Same as pygame.sprite.Group`
-
-   This class is an alias to ``pygame.sprite.Group()``. It has no additional functionality.
-
-   .. ## pygame.sprite.RenderClear ##
-
 .. class:: RenderUpdates
 
    | :sl:`Group sub-class that tracks dirty updates.`
@@ -380,18 +364,6 @@ Sprites are not thread safe. So lock them yourself if using threads.
 
    .. ## pygame.sprite.RenderUpdates ##
 
-.. function:: OrderedUpdates
-
-   | :sl:`RenderUpdates sub-class that draws Sprites in order of addition.`
-   | :sg:`OrderedUpdates(*sprites) -> OrderedUpdates`
-
-   This class derives from ``pygame.sprite.RenderUpdates()``. It maintains the
-   order in which the Sprites were added to the Group for rendering. This makes
-   adding and removing Sprites from the Group a little slower than regular
-   Groups.
-
-   .. ## pygame.sprite.OrderedUpdates ##
-
 .. class:: LayeredUpdates
 
    | :sl:`LayeredUpdates is a sprite group that handles layers and draws like OrderedUpdates.`

src_py/sprite.py

@@ -655,8 +655,24 @@ def __init__(self, *sprites):
         self.add(*sprites)
 
 
-RenderPlain = Group
-RenderClear = Group
+class RenderPlain(Group):
+    def __init__(self, *sprites):
+        super().__init__(*sprites)
+        warn(
+            "This class will be removed in version 2.4.0",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+
+
+class RenderClear(Group):
+    def __init__(self, *sprites):
+        super().__init__(*sprites)
+        warn(
+            "This class will be removed in version 2.4.0",
+            DeprecationWarning,
+            stacklevel=2,
+        )
 
 
 class RenderUpdates(Group):
@@ -690,31 +706,15 @@ def draw(self, surface):
 
 
 class OrderedUpdates(RenderUpdates):
-    """RenderUpdates class that draws Sprites in order of addition
-
-    pygame.sprite.OrderedUpdates(*sprites): return OrderedUpdates
-
-    This class derives from pygame.sprite.RenderUpdates().  It maintains
-    the order in which the Sprites were added to the Group for rendering.
-    This makes adding and removing Sprites from the Group a little
-    slower than regular Groups.
-
-    """
-
     def __init__(self, *sprites):
-        self._spritelist = []
-        RenderUpdates.__init__(self, *sprites)
-
-    def sprites(self):
-        return self._spritelist.copy()
-
-    def add_internal(self, sprite, layer=None):
-        RenderUpdates.add_internal(self, sprite)
-        self._spritelist.append(sprite)
-
-    def remove_internal(self, sprite):
-        RenderUpdates.remove_internal(self, sprite)
-        self._spritelist.remove(sprite)
+        super().__init__(*sprites)
+        warn(
+            "OrderedUpdates is now just an alias to RenderUpdates, order of "
+            "sprites is now maintained in all sprite Group classes. This "
+            "class will be removed in version 2.4.0",
+            DeprecationWarning,
+            stacklevel=2,
+        )
 
 
 class LayeredUpdates(AbstractGroup):