Make neurons from Decision Making tutorial much faster with GraphDynamics

[MasonProtter]

So this does away with the composite events for the LIFExci and LIFInh neurons, and the connection-based events that I was originally using, in favour of a new concept where each event is given an object foreach_connected_neuron which can be used to apply a function to every downstream connected neuron from a given neuron.

This turns out to be much faster than what I was doing before. For example, before I had something like

julia> decision_making_bench(N_E=100; mtk=false, parallel=true)
GraphDynamics.jl Serial:        
  time to construct Problem:   0.432885 seconds (4.14 M allocations: 199.099 MiB)
  time to first solve:        84.367572 seconds (91.81 M allocations: 6.094 GiB, 2.62% gc time)
  compiled solve time:        83.887199 seconds (91.81 M allocations: 6.094 GiB, 2.17% gc time)

GraphDynamics.jl Parallel:  
  time to first solve:        71.096560 seconds (307.66 M allocations: 26.199 GiB, 9.28% gc time, 16.55% compilation time)
  compiled solve time:        58.812354 seconds (260.36 M allocations: 23.974 GiB, 10.07% gc time)

vs after:

julia> decision_making_bench(N_E=100; tspan=(0.0, 30.0), mtk=false, parallel=true)
GraphDynamics.jl Serial:        
  time to construct Problem:   0.126195 seconds (1.61 M allocations: 82.515 MiB)
  time to first solve:         3.096629 seconds (5.27 M allocations: 441.201 MiB, 1.79% gc time, 13.37% compilation time: 100% of which was recompilation)
  compiled solve time:         2.810533 seconds (4.25 M allocations: 389.574 MiB, 6.47% gc time)

GraphDynamics.jl Parallel:  
  time to first solve:        13.001428 seconds (55.67 M allocations: 3.094 GiB, 6.22% gc time, 87.11% compilation time)
  compiled solve time:         1.733313 seconds (9.26 M allocations: 933.787 MiB, 9.55% gc time)

This PR requires Neuroblox/GraphDynamics.jl#10 and Neuroblox/GraphDynamics.jl#9 which should be on the general registry as v0.2.0 soon.

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Edit:

julia> decision_making_bench(N_E=1500; tspan=(0.0, 30.0), mtk=false, parallel=true)
GraphDynamics.jl Serial:        
  time to construct Problem:  33.021983 seconds (259.92 M allocations: 11.507 GiB, 19.54% gc time)
  time to first solve:       742.163511 seconds (98.22 M allocations: 8.721 GiB, 0.28% gc time)
  compiled solve time:       744.091654 seconds (98.22 M allocations: 8.721 GiB, 0.24% gc time)

GraphDynamics.jl Parallel:  
  time to first solve:       155.421290 seconds (105.55 M allocations: 9.543 GiB, 1.21% gc time)
  compiled solve time:       158.298079 seconds (105.55 M allocations: 9.543 GiB, 1.12% gc time)