public int scaleToFitSquare (int width, int height, int numChars) {
        return Math.min(scaleForPixelHeight(height), scaleForPixelWidth(width, numChars));
    }
Uses max advance, ascender and descender of font to calculate real height that makes any n glyphs to fit in given pixel
width and height.
@param width the max width to fit (in pixels)
@param height the max height to fit (in pixels)
@param numChars max number of characters that to fill width
core/src/com/badlogic/gdx/graphics/g2d/freetype/FreeTypeFontGenerator.java