This reverts #1029. As raised in #1097, the formatting chosen doesn’t
work well when doing math. There may be a way to balance compatibility
with multiple format styles with handling non-currency amounts
correctly, but it will require some more careful consideration. Re-opens
#894.

Added onboarding and budget e2e tests. Also fixed an issue for
first-time flows using imports: currently people end up with a blank
white screen after importing. Instead they should see the budget table.

Related: https://github.com/actualbudget/actual/issues/583