Number of Decimals setting is not used anymore

[martynasbakanas]

User Story

As a admin, I want decimal config be working in frontend.

Details

In plugin currency setting we have Number of Decimals config. If I set it to 0, in frontend it still shows 2 decimal places.
I see that useCurrencyFormater is DonationAmountLevels and it uses Intl.NumberFormat which accepts minimumFractionDigits option.
This option is used in Currency Switcher already so it should be implemented and used in other amount fields.

Expected Behavior

Number of Decimals actually does what it is supposed to do

Steps to Reproduce

1. Create a form
2. Make Number of Decimals setting 0 or 1
3. Add form to page
4. See that form amount decimals are not the same as in settings

Acceptance Criteria

• Number of Decimals actually does what it is supposed to do