Add ImageText use_max_line_height()

[radarhere]

Helps #1646. Alternative to #9581

Currently, the bottom of the bounding box of the text "A" is used to determine text line height.

#1646 found that other characters may have larger text height, leading to overlap between lines of text. While this is hard to see with most fonts, I found Great Vibes.

from PIL import Image, ImageDraw, ImageFont, ImageText
font = ImageFont.truetype("Tests/fonts/GreatVibes-Regular.ttf", 120)
text = ImageText.Text("adjust\nYellow", font)

im = Image.new("RGB", (309, 306))
draw = ImageDraw.Draw(im)
draw.text((0, 0), text, "#ff0")
im.save("before.png")

gives

This PR adds use_max_line_height() to ImageText. If I call that, the largest bounding box from all of the characters in the given text is used (not all possible characters of the font). Using that method, I get