[FEATURE] Add method for fetching single record

Introduce a method for retrieving a single record, similar to
t3lib_DB::exec_SELECTgetSingleRow().

Resolves: #56087
Releases: 2.3
Change-Id: I9a4562e5e6501557fd69f43d9aff8d07a6973461
Reviewed-on: https://review.typo3.org/29959
Reviewed-by: Francois Suter
Tested-by: Francois Suter