[2] Allow "single" change of Fee asset on TX

My own opinion is that it would be nice to have a "change fee asset directly" when yo do a transaction, that doesn't stick to be the default, but just for that one op. But that's for a followup issue I think.

_Originally posted by @startailcoon in https://github.com/bitshares/bitshares-ui/issues/1117#issuecomment-512752150_

With the new Fee selection component we can now let the user select the default fee asset in a nice view. At the moment we have not enabled this feature directly on the Transaction confirmation itself, which would be a nice addition.


Related are https://github.com/bitshares/bitshares-ui/issues/1498

Start by reviewing the existing Fee selection component and the transaction confirmation flow, then compare the related issue 1498. The work is done when confirmation lets a user select a fee asset for that transaction without changing the default selection.

Written by the indexing model from the issue text.