[Scheduling] Add interfaces to allow removal of problem components and properties

Currently, `Problem` instances can only be constructed (by adding operations/operator types/dependences), but neither these components nor the properties set for them can be removed again afterwards. We should add methods to allow this modification across the problem hierarchy, and update the documentation accordingly.

Start by tracing the Problem hierarchy and the existing interfaces used to add operations, operator types, dependences, and their properties. Define the removal scope across that hierarchy, then update the documentation and verify that each newly supported component and property can be removed.

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