Add the possibility to simulate phase-type distributed sojourn times in the LCT model

[lenaploetzke]

Feature description

By allowing non-identical transition rates between the subcompartments, hypoexponentially distributed sojourn times can be allowed. By adding other possible paths / transitions, one could also represent general phase-type distributions (e.g. allow the path E_1 to E_3 etc.). Phase-type distributions are well suited for approximating general distributions:

As the phase-type distribution is dense in the field of all positive-valued distributions, we can represent any positive valued distribution. (https://en.wikipedia.org/wiki/Phase-type_distribution, have to search for a reliable source)

For this, a general matrix for the transitions between subcompartments might have to be permitted, so that, for example, a flow from E_n to E_1 is also possible (depending on the selected distribution).

See also e.g. P. J. Hurtado und C. Richards, „A procedure for deriving new ode models: Using the generalized linear chain trick to incorporate phase-type distributed delay and dwell time assumptions“, Mathematics in Applied Sciences and Engineering, 2020. https://doi.org/10.5206/mase/10857.

The programming implementation should not be complex. For TimeExposed etc. matrices should be used instead of the ScalarTypes.

Additional context

No response

Checklist

• [X] Attached labels, especially loc:: or model:: labels.
• [X] Linked to project.