Bug 34946: Remove the use of event attributes from self checkout and check-in

Bug 34946: Remove the use of event attributes from self checkout and check-in

This patch removes the use of event attributes from the self checkout
and self check-in templates. These events are defined now along with the
other in-page JS.

To test you must have SelfCheckInModule and WebBasedSelfCheck
preferences enabled. And SelfCheckoutByLogin = cardnumber.

- Navigate to the self checkout interface
  (/cgi-bin/koha/sco/sco-main.pl).
- When the page loads, cursor focus should be automatically placed in
  the barcode field.
- Test the "munge history" feature from Bug 10016:
  [1] Start a web-based self-check session.
  [2] Enter a patron barcode.
  [3] Allow the self-check session to time out.
  [4] Use the back button.  You should get the patron barcode
      entry form; you should not be prompted to resubmit form input.
  [5] Enter a patron barcode, perform some transactions, then
      use the finish button.
  [6] Next, use the back button.  You should get the patron barcode
      entry form.
- Test the updated checkout_confirm function by submitting the "magic"
  barcode for checkout: __KOHA_NEW_CIRC__. The user's session should be
  ended.

- Navigate to the self check-in interface
  (/cgi-bin/koha/sco/sci-main.pl).
- Test the cursor focus and "munge history" feature on this page too.

Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>