User-Provided Function Context

A RIR function (ie. a DispatchTable) should have a user-provided context, that is a minimal context required to enter a function. This needs:

1. Add a Context to the dispatch table
2. Add a api to set a context on the dispatch table (for now this can be very simple, e.g. just the numerical representation of a context) related: #911
3. Ensure the context is checked when calling the function (should be enough to check in dispatch in interp.cpp)
4. Ensure the context is checked when entering an inlined section of the function