Query for programmable tokens at an address

[j-mueller]

[ ] Add a query to Wst.Offchain.Query that returns the amount of programmable tokens belonging to an address.
[ ] Add a test for this to one of the existing unit tests, such as issueAlwaysSucceedsValidator.
[ ] Add a GET route to Wst.Server.Types.QueryAPI and implement it in Wst.Server

This can be done using Wst.Offchain.Query.programmableLogicOutputs, filtering the outputs to those with the correct payment credential, and summing up the results by monetary policy. (Output should be something like Map PolicyId Quantity)