Remove L0 from MicroDST

L0 is obsolete LHCb!2735 (merged) . Remove all L0 from MicroDST writers.

This builds in lhcb-run3-cleanup.

Question: why is MicroDST/MicroDSTAlgorithm/CopyCaloAdcs.* not in MicroDST/MicroDSTAlgorithm/src/ ?