Add signals to mouse interaction for Control, Sprite2D and AnimatedSprite2D

[azur-wolve]

To know if the mouse has clicked or is hoviring a Sprite2D, or the current frame of an AnimatedSprite2D, a lot of t workaround is necessary.

for a Sprite2D:

if my_sprite.get_rect().has_point( to_local( get_global_mouse_position() )):
#      do whatever

for an AnimatedSprite2D:

var frame_sprite := Sprite2D.new()

frame_sprite.texture = anim_sprite.sprite_frames.get_frame_texture( anim_sprite.animation, anim_sprite.frame )

if frame_sprite.get_rect().has_point( to_local( get_global_mouse_position() )):
#     do whatever

yes can be done, but thats a lot to only check for mouse interaction with a sprite
as its something of generic use should be core

Proposals:

• built-in signals: mouse_entered, mouse_exited, mouse_hover, mouse_clicked (Control could benefit as well)
• ability to only take into account non-transparent regions of the Texture2D