Revert "[TASK] Rebuild the calcAge functionality"

This change was considered to need some more work during
mrge post review:

* 6.2 version adds not allowed deprecations to a released branch
* It adds two arbitrary (public) constants CEIL and FLOOR
* Method names need improvement
* Violation of single responsibility
* The static utility class has dependencies
* The patch adds another "always loaded" file to main bootstrap
* Undocumented (minor) breaking changes
* (Minor) code style issues

Reverted: #20016
Releases: 6.3, 6.2

This reverts commit 98c0ff7144a67ce8780a1b1ebe55749b6909e202
Change-Id: I7b07f2176eae78f6000db685c0f54164d5040202
Reviewed-on: https://review.typo3.org/31236
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn