[TASK] Cleanup indexed_search

The ext can be cleaned up a bit:
* Remove not needed/old files
* Remove namespace compatibility for example files

Change-Id: I50ae60217c186f069908963aa2670d23c1fbe41e
Resolves: #42513
Releases: 6.0
Reviewed-on: http://review.typo3.org/16038
Reviewed-by: Wouter Wolters
Reviewed-by: Mattias Nilsson
Reviewed-by: Philipp Gampe
Reviewed-by: Felix Kopp
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel