[BUGFIX] Extbase Plugin for Indexed Search not working

The plugin uses wrong classes in several places, which leads to fatal
errors because of missing functions.

Replace all occurences with the right classes.

Resolves: #45162
Releases: 6.1, 6.0
Change-Id: Ie7a0ba25adadf5482b22eaf38c0cf88aaf44cd1a
Reviewed-on: https://review.typo3.org/19254
Reviewed-by: Matthias Nitsch
Tested-by: Matthias Nitsch
Reviewed-by: Benjamin Mack
Tested-by: Benjamin Mack