Button: Width should be dynamically determined depending on the text

[edizcelik]

We currently predefine the width of the buttons (i.e. setting the width as 120px with CSS), however, we should instead set padding of buttons and let the element decide what its width would be depending on the provided children to Button component and the defined paddings. When displaying the spinner, the button should stay at the same width as if the text was visible instead of shrinking its width down.