Replace local "commodity" components with those from general-cores

rtl/VME_SharedComps.vhd defines several "commodity" components (metastability chains, edge detectors etc), which are also available from general-cores.

The core should be updated to use the ones from general-cores and rtl/VME_SharedComps.vhd should be removed from the repository.

Care should be taken with the timing after the update. Since the current implementation puts edge detection after syncrhonization, there will be less wait cycles when we switch to general-cores (since the synchonizers have built-in edge detection between the 2nd and 3rd flip-flop).