Move the `isNonEmptyString` util into a more accessible file.

The following discussion from !10461 (merged) should be addressed:

• @farias-gl started a discussion: (+1 comment)

  This looks like a super generic and useful util function. Should we place it here in the security reports store util file, or should we place it in a more general gitlab util file. (if we already have one).

  I leave it up to you.

  Looks good to me otherwise!