Allow for dependence on discrete choices in stochastic transitions

[timmens]

In this PR, I adjust the stochastic state transitions to allow for dependence on discrete choice variables.

Specifically, I

1. Add the choice grids when computing next_weights (see changes in src/lcm/model_functions.py)
2. Add a state transition that depends on a discrete choice to the stochastic example models and extend the test

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (3195dc8) 98.07% compared to head (cf34ca0) 98.07%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #53 +/- ## ======================================= Coverage 98.07% 98.07% ======================================= Files 45 45 Lines 2491 2491 ======================================= Hits 2443 2443 Misses 48 48 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.