RFC - definition of a runner class using as much of the existing code as possible

[syntron]

Content (lots of changes / these will be splitted into several PRs if the general approach is approved):

• OMCSession.py: rename real OMCPath* classes as privat (start with '_')
• OMCSession: define OMCPathDummy and OMCSessionDummy => no OMC server
• ModelExecution.py: include all code related to model execution (from OMCsession*; ModelicaSystemCmd)
• ModelicaSystemDoE.py: seperate file for this class
• ModelicaSystemDoE.py: use ModelicaSystem / reduce number of arguments to init
• ModelicaSystem(Base).py: split getOutputs() and getContinuous() to Initial and Final data
• ModelicaSystem(Base).py: getOutputs*() / getContinuous*() - always return np.float64
• ModelicaSystemBase.py: define a basic version of ModelicaSystem
• ModelicaSystemRunner.py: definition of a 'runner' class using ModelicaSystemBasic / OMCSessionDummy (see PR Enable the usage of a pre-built model executables by ModelicaSystemRunner #401)
• test_ModelicaSystemRunner.py: test case for ModelicaSystemRunner
• test_*: update of test cases based on above listed changes

Compared to PR #401 this solution:

• still uses the existing OMPython requirements (dependencies of the Runner class; i.e. numpy, etc.)
• shares nearly all code with the current definitions (by using OMCPathDummy and OMCSessionDummy)
• uses | instead of Union

Further changes could do additional modifications such that the 3rd party packages (ZMQ) are not needed at all in the runner code path.

All tests are running without error / tested in https://github.com/syntron/OMPython/actions/runs/20865402893

Please comment!

[syntron]

Some status update on this PR - the main points are:

• Define a runner functionality which allows to run compiled (binary) models without OMC (see PR Enable the usage of a pre-built model executables by ModelicaSystemRunner #401 / @joewa)
• Allow compatibility with OMPython 4.0.0 by defining a support layer on top of the latest code (see [OMCSession*] renames #384 (comment); @casella)

The code defined here updates the internal structure of OMPython such that:

• generic code is separated in ABC classes
• derived code exists for OMC usage and Runner usage
• a compatibility layer exists such that the interface of OMPython 4.0.0 is (basically) supported; this is tested using the original unittests from v4.0.0

Furthermore, as OMCPath is working only for Python >= 3.12, another dimension exists. There is a dummy implementation of OMCPath for Python < 3.12 such that most of the functionality can also be used here. See PR #401 for a hint that even older Python version are used (Python 3.10 or even lower).

These changes could be the baseline for a new documentation (see https://openmodelica.org/doc/OpenModelicaUsersGuide/latest/ompython.html). My idea was to include these changes as 4.x.0 and create a cut at the next release (or keep some kind of compatibility layer alive).

(partly from the discussion in PR #387)

[syntron]

The failed test is due to Windows - it runs well for v4.0.0 (see: https://github.com/syntron/OMPython/actions/runs/21842400755) and 4.x.x (see: https://github.com/syntron/OMPython/actions/runs/21841418638)