[Privacy] Allow disabling third party calls

[nahuhh]

Quotes are from Community-Dev

1. No Frills Mode off. Default. Normal behavior as currently. CounGecko and ChangeNOW calls made as normal at the start of the app for a seamless experience.

Changenow should not be.

2. No Frills Mode partial on. ChangeNOW isn't polled for rates on app start up, but only when one goes into the exchange tab. This will make exchanges take a bit longer while rates are fetched, but limits calls.

This is a sane default

3. No Frills Mode fully on. No external third-party calls are ever made. Exchange functionality broken. CoinGecko rates not shown.

No frills mode fully on should:

• Remove/hide ui element for exchange tab
• exchange rate option for on demand (only pulls rates when manually refreshed)

4. Custom. User can choose which third-party calls are made and when.

Probably my favorite (and the easiest option to implement?)

Privacy setting to disable

• Exchange rates (coingecko)
• Default nodes
• as per # 2, changenow should never be called at launch

[rehrar]

Solved in release 1.5.7.