Double max number of hits in a VP track

Goes together with LHCb!3095 (merged)

Current maximum is 26 but recent improvements in full version of the reconstruction algorithm may lead to 2 hits for a given plane and thus more than 26 hits in total. This led to crashes in the Alignment code.

This needs to be carefully checked for performance. Indeed it could significantly speedup the HLT1. if this is the case, we'll have to see how to have different solutions for HLT1 and Alignment