Draw progress bar when ProgressBarRenderer.IsSupported is false

[HebaruSan]

Problem

After #4255, my Ubuntu VM still had problems rendering LabeledProgressBar. An exception was thrown and the progress bar appeared as a white background with a red X on it.

Cause

ProgressBarRenderer has a boolean IsSupported property which is set based on the capabilities and configuration of the host system. If false, then the class's drawing methods throw exceptions instead of drawing. It must have been true on my main Ubuntu system, but it's clearly false in my VM.

Changes

Now if ProgressBarRenderer.IsSupported is false, we draw it with the PaintEventArgs.Graphics object instead of ProgressBarRenderer.