Make Rect2.encloses return true on same size

[AlexHolly]

fix #26615

func _ready():
	assert(Rect2(0,0,0,0).encloses(Rect2(0,0,0,0)))
	assert(Rect2(0,0,2,2).encloses(Rect2(0,0,2,2)))
	assert(Rect2(0,0,2,2).encloses(Rect2(1,1,1,1)))
	assert(Rect2(0,0,2,2).encloses(Rect2(1,1,0.9,0.9)))

[aaronfranke]

This is probably a good change.

Note that the title is a bit inaccurate, in reality it changes behavior for when the end corner/edges (calculated from position+size) are in the same position, not just when the rects are the same size.

[fossegutten]

Great! Now I can make tetris without major headaches 😂

[akien-mga]

Thanks!