Handle events with time-based triggers without rootfinding?

[dweindl]

We wouldn't really need any of sundials' rootfinding for handling events with time-based triggers.

Handling those events without rootfinding should be more efficient and solve some of those issues:

Cvode routine CVode returned a root after reinitialization. The initial step-size after the event or heaviside function is too small. To fix this, increase absolute and relative tolerances! failed with error code 2

Not yet sure how much effort it would be.

[dweindl]

• Events that trigger at a single constant (non-parameter-dependent) timepoint (Handle events occuring at fixed timepoints without root-finding #2227)
• Events that trigger at a single constant parameter-dependent timepoint (Handle state-independent, parameter-dependent event triggers without root-finding #2913)
• ... (probably not worth the extra effort)

[dweindl]

• Events that trigger at a single constant parameter-dependent timepoint

After #2721:

• add some function to amici::Event to compute the trigger time based on p and k where possible.
• Remove state_independent_events from the amici::[DAE,ODE]Model ctors.
• Ideally, remove Model::state_independent_events_ completely.

EDIT: -> #2913