Fix content centering inside CallIconButton

[rickycheah]

For the Button component, className changed form w-12 to w-fit to allow enough margin numbers with higher digit count.

For elements inside the Button, added h-4 to normalize the height of the button because ChatCenteredDots and "𝑓" have different heights.

When showing ChatCenteredDots or "𝑓", added mx-1 to add margin and center the element horizontally.

The "𝑓" symbol itself is not centered vertically (see image in link), added position: relative; to center it vertically.

<img width="350" alt="image" src="https://github.com/oughtinc/ice/assets/49166991/d5da90b8-a644-4b7a-be62-a479324d2cb9">

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[rickycheah]

I have read the CLA Document and I hereby sign the CLA

[stuhlmueller]

Thank you!