Format numbers, amounts, totals and sums of tokens consistently

[ricburton]

We should try to take into account assets’ prices and amounts when presenting the numbers that comprise balances.

$3k ETH needs more decimal places for the amounts of the token than $0.48 GRT.

This feels like a good framework for when to truncate and when to expand on numbers.

The quick fix is to apply this to the Balances section inside the wallet screen.

The longer fix is a consistent approach to number formatting, fiat currency values, and token prices.

I like to use SF Mono Light for prepended currency symbols and everything after the decimal place.

I use SF Mono Medium for the meat of a number.