A class that holds the interception (and decoration) contexts which are currently in progress.
An interception context is a set of
CombinedInterceptorAndDecoratorStackMethodHandler
references for which interception is currently
suppressed (so that self-invocation is not possible).
Such references are added as soon as a CombinedMethodHandler is executed in an interception context that
does not hold it.
Classes may create new interception contexts as necessary (e.g. allowing client proxies to create new interception
contexts in order to make circular references interceptable multiple times).