Use event-local memory pool in LHCb::Pr::Muon::PIDs and muon decoding

Adds event-local memory pool support to LHCb::Pr::Muon::PIDs and muon decoding classes. Enables use of it in the decoding (if it's enabled in the scheduler).

Also adds a helper LHCb::make_object_array<T, N>( args... ) that returns std::array<T, N> where each of the N objects of type T is [explicitly] initialised with args....

Targets the branch of !2270 (merged) so the diff is correct. Hopefully we can merge that one imminently; for now this makes the diff appear correctly.

cc: @sstahl @rvazquez