fix: title screen particle burst effect never working correctly

[camping6464]

effects.rpy

Using the animation timebase for the SpriteManager in ParticleBurst causes the particles to always despawn prematurely, one frame after being generated. Setting the animation parameter to False in the SpriteManager() initialization fixes the issue by giving it its own timer that starts at 0 instead of relying on the timer from the image or transform animation that calls the SpriteManager.

splash.rpy

The particle burst effect always play again each time the user re-enters the title screen, even from another screen of the main menu. Moving the ParticleBurst().sm call out of image menu_particles and inside transform emit_particles (formerly known as transform particle_fadeout) fixes the issue and makes the effect play only once as long as the user is still in a screen part of the main menu, similarly to transform menu_art_move().

The pause timer from image menu_particles has also been moved to transform emit_particles to potentially avoid unnecessary uses of an animation pause timer when nothing is supposed to happen afterwards.