Properly fix handling of Clocks the front-end, back-end and codegen

[Adrian Pop]

See PR:
​https://github.com/OpenModelica/OMCompiler/pull/1574

Currently we force in the front-end:

• evaluation of solverMethod in Clock (Static.mo)
• vectorization of clock operators (Static.mo)

because:

• back-end does not evaluate the solverMethod
• the C++ runtime does not support non-vectorized clock operators

This ticket is for fixing these issues:

1. revert PR ​https://github.com/OpenModelica/OMCompiler/pull/1574
2. implement evaluation of clocks in SynchronousFeatures.resolveClocks
3. add proper support for non-vectorized clocked operators in the C++ runtime

[Adrian Pop]

@sjoelund.se: are you sure we don't need vectorization of clock operators in the fron-end? As far as I can tell the specification says that interval takes a clock not an expression.

[Martin Sjölund]

For interval:

This operator returns the interval between the previous and present tick of the clock of the expression, in which this operator is called and the clock of the optional argument u.

u can be an array, but interval always returns a Real value, never an array. Bernhard read the specification wrong and implemented the operators to vectorize for clocked expressions.

A possible fix to be more similar to what we had before would be to add Evaluate=true to the solverMethod input argument and adapt the frontend to evaluate this input although I would prefer the backend since the frontend cannot always evaluate expressions.

[Bernhard Thiele]

After discussing it with Martin I created a Modelica ticket for discussing/clarifying this issue (​https://trac.modelica.org/Modelica/ticket/2161).

[Francesco Casella]

Mostly obsolete, can be considered as a duplicate of ​https://github.com/OpenModelica/OpenModelica/issues/7854.

See also GitHub ticket ​https://github.com/OpenModelica/OpenModelica/issues/4363