[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: I446be223e48dc7fc6de78a6d17eb0b1923108409
Reviewed-on: https://review.typo3.org/18020
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Matthias Nitsch
Tested-by: Matthias Nitsch
Reviewed-by: Wouter Wolters
Reviewed-by: Stefan Neufeind
Reviewed-by: Marc Hirdes
Tested-by: Marc Hirdes
Tested-by: André Haehnel
Reviewed-by: Benjamin Mack
Tested-by: Benjamin Mack