Setter for Arc.angle incorrect

[bablokb]

Commit 7f83f59 added a setter for Arc.direction, but made the direction depend on Arc.angle. But these two attributes are
independent.

https://github.com/adafruit/Adafruit_CircuitPython_Display_Shapes/blame/e8867231041837735ef2769a6dc793887d1979ca/adafruit_display_shapes/arc.py#L148

    @direction.setter
    def direction(self, value):
        self._direction = value
        self._direction = value - self.angle / 2
        self._init_arc()

This also results in weird shapes being drawn. Removing the second line make arc work again.

[bablokb]

I was wrong: the setter for direction does have to correct for angle. But the setter for angle must also correct the direction (taking the old value into account).

N.B: the reason that I don't create a PR is simple: all these setters are extremely inefficient if you need to set more than one property. It is far easier to just create a new arc providing all the properties at once.