Add clang16 to DaVinci/v64r7

Add a clang16 build for DaVinci v64r7. Lower memory use, helps with productions. FYI @msaur @cburr @nskidmor

Release checklist (to be filled by the shifter)

• release build validation (to be checked with the MR author)
• RPMs deployment
• CVMFS installation
• web pages update