Performance improvement on application form (#3577)

This PR optimizes the code and logic responsible for unlocking
the application form on detecting human activity.

- makes the unlocking action DRY.
- move away from using jquery
- prevent the unlock action from firing on every mouse move, the unlock
  action is performed only once.
- Use more standard key names instead of keycodes.

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Co-authored-by: Fredrik Jonsson <frjo@xdeb.org>