[BUGFIX] Fix parse time calculation

Parse time calculation in RequestHandler was wrong,
additionally the same calculation is used in admin panel view.

The calculation was therefore added to the TimeTracker into a
common function and tested.

Change-Id: Ib935664e78a62deab7818426e2a853087c00b015
Resolves: #80742
Releases: master, 8.7
Reviewed-on: https://review.typo3.org/52727


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Reviewed-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Alexander Opitz <opitz.alexander@googlemail.com>
Tested-by: Alexander Opitz <opitz.alexander@googlemail.com>