[FEATURE] ImageViewHelper removed title fallback onto alt tag

Currently the title tag is customizable but, if not set, the value
of the alt tag will be used. But sometimes you don't want to render
a title tag.

This patch removes the fallback onto the alt tag value and make the
title tag optional.

Releases: 6.2
Resolves: #47552
Change-Id: I7a2415422be3da2b9f81c7e29a4e96507a1ad69e
Reviewed-on: https://review.typo3.org/20347
Reviewed-by: Stefan Froemken
Tested-by: Stefan Froemken
Reviewed-by: Daniel Hürtgen
Tested-by: Daniel Hürtgen