Add "clicks" to mouse event

[Starbuck5]

Description

In SDL2 and SDL3, mouse button events come with a "clicks" member "1 for single-click, 2 for double-click, etc."

https://wiki.libsdl.org/SDL2/SDL_MouseButtonEvent
https://wiki.libsdl.org/SDL3/SDL_MouseButtonEvent

This seems useful, we should expose it in pygame-ce.

Shoutout to pykraken for having this implemented in their code :D

[JReesW]

I will give this a proper shot this week

[JReesW]

See PR #3712