Follow-up from "[EE] Support unlimited file search in web UI and API"

The following discussion from gitlab-ee!8671 should be addressed:

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

  Wiki blobs are search slightly differently - I didn't investigate this further so I kept the limit here (originally it was inherited from FileFinder)

Update: This should be mostly a testing and pretty simple task: create many wiki blobs (tens of thousands), test that WikiFileFinder#search_filenames performs reasonably well after removing the BATCH_SIZE limit.