Switch to multi-simulation adapters by default

[Helveg]

Describe the work done

Breaking change: The adapter.simulate and adapter.run signatures are now expected to handle vararg *simulations, and to return an array of results. Passing multiple simulations should try to run these simulations in the same "world" (e.g. for NEURON/NEST to simply instantiate all given simulation components into global state, so that they run simultaneously, and for Arbor to compose and run the recipes)

List which issues this resolves:

• @Geenetto required a forward/inverse double scaffold simulation setup

Tasks

• [x] Added tests
• [ ] Updated documentation

[codecov[bot]]

Codecov Report

Attention: 29 lines in your changes are missing coverage. Please review.

Comparison is base (3ff5268) 83.81% compared to head (8c0fb34) 83.76%.

Files	Patch %	Lines
bsb/simulation/adapter.py	59.09%	18 Missing :warning:
bsb/reporting.py	33.33%	6 Missing :warning:
bsb/simulation/_backends.py	62.50%	3 Missing :warning:
bsb/option.py	33.33%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #804 +/- ## ========================================== - Coverage 83.81% 83.76% -0.06% ========================================== Files 105 105 Lines 12977 13008 +31 ========================================== + Hits 10877 10896 +19 - Misses 2100 2112 +12 ```

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