Add numeric solver to synapses

[pnbabu]

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[github-actions]

Bencher Report

Branch	1208/merge
Testbed	ubuntu-latest

🚨 1 Alert

Iteration	Benchmark	Measure Units	View	Benchmark Result (Result Δ%)	Upper Boundary (Limit %)
0	tests/nest_continuous_benchmarking/test_nest_continuous_benchmarking.py::TestNESTContinuousBenchmarking::test_stdp_nn_synapse	Latency seconds (s)	📈 plot 🚷 threshold 🚨 alert (🔔)	3.88 s (+13.04%) Baseline: 3.43 s	3.78 s (102.76%)

Click to view all benchmark results

Benchmark	Latency	Benchmark Result seconds (s) (Result Δ%)	Upper Boundary seconds (s) (Limit %)
tests/nest_continuous_benchmarking/test_nest_continuous_benchmarking.py::TestNESTContinuousBenchmarking::test_stdp_nn_synapse	📈 view plot 🚷 view threshold 🚨 view alert (🔔)	3.88 s (+13.04%) Baseline: 3.43 s	3.78 s (102.76%)

Benchmark	Latency	Benchmark Result seconds (s) (Result Δ%)	Upper Boundary seconds (s) (Limit %)
tests/nest_continuous_benchmarking/test_nest_continuous_benchmarking.py::TestNESTContinuousBenchmarking::test_stdp_nn_synapse	📈 view plot 🚷 view threshold 🚨 view alert (🔔)	3.24 s (-5.50%) Baseline: 3.42 s	3.77 s (85.91%)

Benchmark	Latency	Benchmark Result seconds (s) (Result Δ%)	Upper Boundary seconds (s) (Limit %)
tests/nest_continuous_benchmarking/test_nest_continuous_benchmarking.py::TestNESTContinuousBenchmarking::test_stdp_nn_synapse	📈 view plot 🚷 view threshold 🚨 view alert (🔔)	3.25 s (-5.05%) Baseline: 3.42 s	3.77 s (86.32%)

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[clinssen]

Could you take care of this TODO?

[pnbabu]

The tolerance is a bit high. The tests fail if I decrease the tolerance. I tried a few things, such as adjusting rtol and atol, but couldn't lower the difference. Do you have any ideas?

[clinssen]

This was a bug, right? How could this ever have worked before?

[pnbabu]

The synapse model used in the test in this PR has variables that strictly belong to the synapse. Hence, I added them to strictly_synaptic_vars in the codegen_opts introduced in #1229.
This then caused the append in the line to create a list of lists, which failed at line:

nestml/pynestml/utils/ast_utils.py

Line 1779 in 81ed384

assert type(var) is str

That's why I changed it to extend. Perhaps we should change all the append calls here to extend instead to avoid errors.

[clinssen]

Could you also update running_nest.rst, especially under the heading "Event-based updating of synapses"? Cheers!