Fmutool

- ADDED: `fmucontainer` supports `-profile` option to expose RT ratio of embedded FMUs during simulation
- ADDED: Ability to expose local variables of embedded FMUs at container level
- FIXED: `fmucontainer` handles missing causality and handles better variability

Fix ModelStructure for fmu_container
Remove python >3.9 specific code

**NEW** : fmucontainer : a new tool integrated into fmutool. This allows to
* group multiple FMUs inside one FMU Container,
* Mutli-threaded execution of `doStep()` ,
* Expose the “signals” between FMU’s as local variables,
* set start values ​​of embedded FMUs,
* handle a specified time_step for the container,
* Container of Container is also working,
* “simple” user interface to build a container.

Curent Limitations :
* Only the co-simulation mode is supported.
* only the version 2.0 of the standard is supported.
* only windows OS is supported.

* ADDED: Ability to add your own FMU Checker.
* ADDED: SaveNamesToCSV will dump scalar types and start values.
* CHANGED: Default (Generic) Checker checks the `modelDescription.xml` conformity against the XSD specification file.