[FEATURE] Substitution of default markers in single function

In the function
TYPO3\CMS\Backend\Utility\BackendUtility::exec_foreign_table_where_query
a lot of default markers (like CURRENT_PID, etc.) are replaced.
It would be useful to have this substitution available as single
function, so that it can be called without executing some query.

Resolves: #21892
Releases: 6.2
Change-Id: I4da8279d1b95566690bb0934ac00299e4f4fee3e
Reviewed-on: https://review.typo3.org/22661
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Nicole Cordes
Tested-by: Nicole Cordes
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring