Center all operation buttons

[tibbi]

especially "X" is not centered vertically

[ismailnurudeen]

This a bit tricky because it isn't that the content of the operation buttons aren't centred but because the operation characters look quite different.

I made a comparison here by putting the "×" operator and "9" in same button to show the alignment.

Trying to fix the alignment by using paddings would mess things up as it will look different based on the screen size.
A possible solution here would be to replace the operation buttons with Icon buttons and use vector drawables.

[zeshansahi]

do the issue fixed or not? I want to work on it.

[tibbi]

you can work on it