[CLEANUP] Add and clean up @var and default values for fields

Fields should have default values to communicate that we
haven't just forgotten them.

This change also adds some missing @var annotations and
some undeclared fields.

Change-Id: I70ed5dc76e98a915566f19bf4f2beb3b4264020d
Releases: 6.2
Resolves: #58084
Reviewed-on: https://review.typo3.org/29668
Reviewed-by: Nico de Haen
Tested-by: Nico de Haen