Rename `scan_result` to `approval` policy in the FE

The following discussion from !150207 (merged) should be addressed:

• @arfedoro started a discussion: (+1 comment)

  suggestion (non-blocking) 🏓

  For the follow-up:

  What do you think about renaming all mock files too? Otherwise it potentially be confusing after some time, when either we forget or new members would work on it.