various fixes for DD4Hep build

Goes with Lbcom!481 (merged), Rec!2070 (merged), Brunel!1019 (merged), Moore!494 (merged), Boole!291 (merged), Alignment!133 (merged) and Panoramix!75 (merged). Based on top of !2579 (merged)

Same as !2563 (closed) but we need it to be applied after !2579 (merged) to avoid conflicts

This is basically trying to have a functional DD4hep backend across the LHCb stack. Not everything is solved yet, but at least the reconstruction is working fully (including HLT2) and Alignment is compiling again.