Random number generators

[Helveg]

Sooner or later I'll have to submit to the numbercrunchers and accomodate finer control over the used RNG.

Simple implementation: Add a new root config dict rng to the config tree that can contain dynamic RNG definitions:

• type: default numpy, but also plugins like the simulators could add extra RNG types to control RNG inside of the simulators.

Then the dynamic numpy RNG contains 2 attributes:

• generator: default default_rng, otherwise the name of the BitGenerator class.
• seed: default None or a seed sequence.

We add a function get_rng to the Scaffold class, which returns the singletons for each configured node, where:

def get_rng(self, node="bsb"):
  if node == "bsb":
    return self.rng.get(node, RandomGeneratorNode())
  else:
    return self.rng[node]

[Helveg]

Related: #183 , #759

[Helveg]

Example configuration:

rng:
  bsb: {}
  numpy:
    generator: Mersenne
  nest:
    master_seed: 1234