[TASK] Provide title attribute for iframes

All iframes must contain a description to allow screen
readers to identify the content or purpose of them.

Therefore all iframes are now equipped with a proper
title attribute, describing their content.

Resolves: #92646
Releases: master, 10.4
Change-Id: I6af29e2587f51c3800c8b7590ed91f57e4fafd20
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/66235


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Josef Glatz <josefglatz@gmail.com>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Josef Glatz <josefglatz@gmail.com>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>