harmonizing grey shades

[RomanKostka]

What should we do?

Harmonize the grey shades we use currently in the form-editor.
Grey shades should be aligned with the greyshades we use in other products (carbon design system colors).
Sidepanels & subheader should all have the same shade of grey (F4F4F4).

Why should we do it?
In order to stay consistent across all applications and to provide no visual distortion because of the use of slightly different grey shades.