Update Zashi Theme

[Milan-Cerovsky]

Is your feature request related to a problem? Please describe.

• Once new zashi theme design system is done remove and replace ExchangeRateColors
• Add dimensions to theme & replace existing ones in exchange rates

[HonzaR]

I'd not necessarily remove it. We could just make this class internal and consume it within the ui-design-lib module, as we do for, e.g., TopAppBarColors or ButtonColors. The main goal of this task should be extracting commonly used colors to values as we do in Colors.kt. See comments here and here.