[TASK] Move ExtJS- & JavaScript from t3lib

Moves JavaScript files and their corresponding includes.
As a result the t3lib directory is removed completely.

Change-Id: I77938f43f15e8293c1439a55b2b7716d764d339b
Resolves: #49342
Releases: 6.2
Reviewed-on: https://review.typo3.org/21595
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring