[Excel Style Filter] Sort and Move buttons should not have elevation/shadow and 4px gap between icon buttons should be added

[yradoeva]

1. The Sort/Move Buttons in the button groups should not be elevated as per design.
   Valid for L, M and S size, light and dark mode.

Steps to reproduce:

1. Open Ignite UI Angular demo repo
2. Open the Grid Column Moving example (or any other with an Excel style filter option)

Result vs. Design:

2. Medium and Small size:

• there should be a 4px gap between the icon buttons (Select Column, Pin Column, Hide Column) at the top of the dialog

Reference: Design UI Kit