Add a drop-down for Tax Auth Combined Id in Product Price Creation screen

Currently in Product Price Creation screen there are 3 fields:

• Tax Auth Geo ID
• Tax In Price
• Tax Auth Combined Id

We should either show only

• Tax Auth Geo ID
• Tax In Price
  using lookups like in Product Store screen and remove the Tax Auth Combined Id field
  or keep it and use a combined Tax Auth Geo ID+Tax In Price drop-down for it. Then we could use the same in Product Store screen to be consistent