PicoDisplay: Fix misalignment on rotated Pico Displays (fixes #562.)

[Gadgetoid]

Test script, modified from the repro provided in #562 -

from picographics import PicoGraphics, DISPLAY_PICO_DISPLAY, PEN_P4
import time


def draw_outline(rotate):
    display = PicoGraphics(display=DISPLAY_PICO_DISPLAY, pen_type=PEN_P4, rotate=rotate)

    W, H = display.get_bounds()
    
    MIN_X = 0
    MIN_Y = 0
    
    MAX_X = W - 1
    MAX_Y = H - 1

    print(W, H)

    RED = display.create_pen(255, 0, 0)
    GREEN = display.create_pen(0, 255, 0)
    BLUE = display.create_pen(0, 0, 255)
    WHITE = display.create_pen(255, 255, 255)
    BLACK = display.create_pen(0, 0, 0)
    
    colours = [RED, GREEN, BLUE, WHITE]

    display.set_pen(BLACK)
    display.clear()
    display.set_pen(colours[rotate // 90])
    display.line(MIN_X, MIN_Y, MAX_X, MIN_Y)
    display.line(MAX_X, MIN_Y, MAX_X, MAX_Y)
    display.line(MAX_X, MAX_Y, MIN_X, MAX_Y)
    display.line(MIN_X, MAX_Y, MIN_X, MIN_Y)
    
    display.text(f"angle: {rotate}", 5, 5)
    
    display.update()


while True:
    for a in [0, 90, 180, 270]:
        print(f"angle: {a} degrees")
        draw_outline(a)
        time.sleep(1)