[CLEANUP] ext_emconf files

Quite some keys in ext_emconf are obsolete and can be removed.
See related issue for a list of keys.

Change-Id: Id12c2e3d61569cc1e84226ef75120ae4261922fb
Resolves: #60128
Related: #58365
Releases: 6.3, 6.2
Reviewed-on: https://review.typo3.org/31397
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Susanne Moog
Tested-by: Susanne Moog
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn