Rely only on `Vector` in case `PartitionedVector` represent a `Vector`

[paraynaud]

In the case an pv::PartitionedVector has pv.simulate_vector == true, then try to use only the Vector pv.epv.v.
In that case, most operations must be reimplemented to distinguish the cases pv.simulate_vector == true and pv.simulate_vector == false.
Also, the broadcast mechanism must be adapted, such that either :

• broadcast between PartitionedVector and Vector is supported
• we identify first that all PartitionedVectors have pv.simulate_vector == true to then apply the broadcast on their respective pv.epv.v.