Implement PEtab v2 import

[dweindl]

We need to revise the PEtab import to handle the upcoming PEtab v2 format.

This implies:

• New parameter mapping
  • instead of "preequilibration" and simulation, there will be a variable number of periods (at first, more than 2 conditions will only be supported through the JAX interface)
  • the mapped values will not be identifier or float, but could also be more complex math expressions
  • the values for reinitialization may depend on the model state and parameters (this also needs to be accounted for when computing sensitivities)
• Auto-upconversion of PEtab v1 problems, to avoid duplicating the import logic
• ...

[dweindl]

The initial import implementation for sundials-based simulations will happen through translating experiments to events (PEtab-dev/libpetab-python#370).

To make that more robust, ideally #2185 should be continued, to support stopping at (constant) parameter-dependent fixed trigger times without root-finding.

Relevant issues:

• SBML import: support for event priorities #2718
• SBML import: support useValuesFromTriggerTime=true #2719
• Handle events with time-based triggers without rootfinding? #2185
• More efficient PEtab parameter mapping #2639
• Clarify steady state simulation & events #2673
• Option to disable event-handling #2386