Propagate CDAssociation modifiers to the respective role symbols

[jra-se]

There are three possible locations to define modifiers in CDAssociations.
However, the Association symbol does not store them.
In fact, the first association modifier seems to be redundant and might even introduce inconsistencies.
With this Pull Request, we propagate the association modifiers to the role symbols.
As a result, the first modifiers becomes a short notation for setting the same modifiers for both roles.
In a second step, we will introduce CoCos to prevent using the first modifier and any of the other two in parallel.

[github-actions]

✔️ Changes pass the MontiVerse

Project	Status

details

Project	Status
montiarc	✅
umlp_experiments	✅
umlp_tool	✅
sd	✅
montifun	✅
fd	✅
automaton	✅
sc	✅
guidsl	✅
artifacts	✅
ocl	✅
od	✅
ucd	⏩
langexperiments	⏩
json	⏩
xml	⏩
cd2gui	✅
mlc	⏩
monticore_future	✅
cd4analysis	✅

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