Data on main chart doesn't update (for ages) when changing currencies

[lyricnz]

1. Open main view in USD: (top of screen) Market cap ~$2b; (first row in table) BTC ~$42.7
2. Hit C 0 (AUD)
3. Market cap immediately changes to $2.7b, BTC takes a minute or two to change
4. Exit and restart, table updated immediately

[lyricnz]

Video of this issue (actually changing AUD->USD)
https://user-images.githubusercontent.com/122371/134755716-bb308d52-819c-4b07-b595-92ad2876cffe.mov
Make more apparent because no visual indicator that a change is pending - see #174

[lyricnz]

Perhaps we could use client-side currency conversion in some cases? This was done recently to work around an API issue
https://github.com/cointop-sh/cointop/pull/209/files#diff-92ed39eadc12477ac0fcd3f82a69a7e9f0f7a6d5f329273c412a76030e74e9ec

[lyricnz]

Caused because the current screen doesn't refresh immediately, but waits for the background refresh to cycle around all the coins. #255

[lyricnz]

Fixed in #232