Sprite module refactoring

[MyreMylar]

This is a topic that has come up several times in the past, the sprite module has some parts that are outdated, some parts that are confusing and a few areas that could be tweaked to improve performance and likely help prepare it for some future refactorings.

I opened a draft PR on this topic back on the upstream repository, but I concluded there that it would be better to break the changes down into a series of smaller and easier to review changes.

GOALS

• Boost sprite group performance in most common looping operations (principally draw).
• Add special_flags support to group draw operations.
• Deprecate & remove from docs redundant Group types (OrderedUpdates is no longer relevant from 3.7 onwards as all python dictionaries are insertion ordered, RenderPlain & RenderClear should also be deprecated as they are just crowding up the docs and source).
• Generally prepare for 'future' upgrades like FRect using sprites and Renderer Texture sharing Sprite Groups.

Refactoring To Do list

• Add image & rect properties to Sprite #1942 - Add .image and .rect to sprite as properties. I'm not sure why these were never attached to the basic sprite class despite being used in every sprite group. They will default to None. Adding them as properties allows us to keep the underlying data types hidden (potentially useful for FRect type usage later), and more importantly lets us attach sprite group operations to them when a new value is assigned to either .rect or .image, which will be important for performance refactors.
• Switching base sprite group container from dictionary to list #2533 Use a 'drawlist' as the basic data type for drawing sprites in all sprite groups. right now only some of the groups store sprites in a list with others making use of a dictionary to do this. Lists are faster to iterate over.
• Switching base sprite group container from dictionary to list #2533 Assemble the drawlist only when changes are made to sprite group's membership or to sprite's .image or .rect properties rather than on every call to draw. This will just improve performance a bit in large groups.
• Undocument and deprecate redundant sprite group classes #2036 - Remove redundant code from OrderedUpdates, add deprecation warnings to it and RenderPlain/RenderClear on creation. Remove all three from docs (? - this last part could wait until the deprecation expires, probably should have a deprecation policy so it is clear).
• use .fblits() to enable support of special_flags parameter in draw, document and test.

I think that is about it. If anyone has any further ideas along the lines of improving what is already here, or removing parts of it for improved clarity (rather than adding new features to the sprite module) then please add a comment.

[itzpr3d4t0r]

switch out .blits() usage for .fblits() usage in sprite groups to enable easy support of special_flags parameter in draw.

About this idk if it's possible since currently we are saving the changed rects blits returns and we wouldn't be able to with fblits since it returns None.