Fix/multiply alpha for table color

[garvittsingla]

Fixes #3205
The main problem was in
MultiplyAlpha for Table<Color>, where only the alpha_blending.opacity was changing but not the color opacity as mentioned itself in the issue

I changed the color alpha itself with the function multiplied_alpha under the AlphaMut trait.
My fix is this:

impl MultiplyAlpha for Table<Color> {
	fn multiply_alpha(&mut self, factor: f64) {
		for row in self.iter_mut() {
			row.element.set_alpha(factor as f32);
			row.alpha_blending.opacity *= factor as f32;
		}
	}
}

Faulty behavior

Change in opacity node before the fill value does not changes anything. The opacity is always full

---

Corrected behaviour

Now changing the opacity changes the color opacity

[0HyperCube]

This is an approach to fixing the issue.

I'm not sure if it is advantageous to have both the alpha_blending.opacity and the element.opacity?

[garvittsingla]

This is an approach to fixing the issue.

I'm not sure if it is advantageous to have both the alpha_blending.opacity and the element.opacity?

@0HyperCube It makes sense, I just don't removed the alpha blending opacity, thought to have a review first

Should i remove it?