bug: VDF not working when using config to configure

[balacmi]

Basically, in the VDFConfigGroup, the modes are initially populated using the Set.of() method, which creates an unmodifiable set. And then the code tries to clear this set when reading from the config file here:

https://github.com/eqasim-org/eqasim-java/blob/953b766d927fe6c117f9473bea9fda2f547fe810/vdf/src/main/java/org/eqasim/vdf/VDFConfigGroup.java#L182

and here:

https://github.com/eqasim-org/eqasim-java/blob/80fa272adfac9827e08d3c3d5f3b6283e820abf2/vdf/src/main/java/org/eqasim/vdf/engine/VDFEngineConfigGroup.java#L40

which causes a java.lang.UnsupportedOperationException.

Probably something like this can be used instead for the initialization of the Set: Set<String> modes = Stream.of("car", "car_passenger") .collect(Collectors.toSet());