Bug 22121: Display 'Price paid' on ILL requests according to CurrencyFormat pref

Bug 22121: Display 'Price paid' on ILL requests according to CurrencyFormat pref

To test:
- Install BLDSS backend
  see: https://wiki.koha-community.org/wiki/ILL_backends
  - Add a new BLDSS ILL request
  - Edit ILL request
  - Fill in Price paid field
  - Verify Price paid is formatted correctly on 'Manage ILL request'
    page

Signed-off-by: Ethan Amohia <ethan.amohia@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(reimplimentation of commit 1493c42e7bae5bffab430072587b7aa0527f6fc7 for 18.11.x series)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>