Calculate text bounds for all baselines

[ystrot]

Currently it works correctly only for top and bottom baselines.

[ystrot]

To resolve this issue we need to update Text.bounds() method. Currently it contains following code:

let size = ...
if (self.baseline == Baseline.bottom) {
    return Rect(x: 0, y: -Double(size.height), w: Double(size.width), h: Double(size.height))
}
return Rect(x: 0, y: 0, w: Double(size.width), h: Double(size.height))

So this method works correctly only when baseline equals to bottom or top. Need to implement corresponding login for alphabetic and mid values. It might be useful to take a look at the TextRenderer.calculateBaselineOffset() method.