Swaps: fix handling of native currency formatting/presentation

[benisgold]

Fixes APP-1346

What changed (plus any additional context for devs)

• created a util to handle formatting of native currency values
• does not handle big numbers, but does not appear to be necessary for the cases where this new util is used
• replaced existing utils convertAmountToNativeDisplay and convertAmountToNativeDisplayWithThreshold
• removed toLocaleStringPolyfill shim since it's broken and no longer needed

Screen recordings / screenshots

https://github.com/rainbow-me/rainbow/assets/15272675/fbee7125-0def-489f-a244-5a9b5680a246

What to test

[linear[bot]]

APP-1346 Switch `.toLocaleString()` to support other nativeCurrencies