Feature Request: Improve RT safe erorr reporting

[tremblap]

Error reporting for realtime (i.e. audio thread) objects could be better, especially for data objects. Problems are:

•  No good way to propagate actual error messages in a RT safe way, many objects just silently fail instead
• For data objects, both RT and NRT, there are a lot of boilerplate checks in every function that actually outweigh the functionally relevant code

Shape of a possible solution

Quite a bit of work required, but would involve

(a) automating away the boilerplate checks that are structurally the same every time: in an ideal world functions dealing with DataSet and friends would just get a valid instance passsed in, and all the checks for validity and availability would have been dealt with upstream
(b) adding some kind of logging in FluidContext that allows RT clients to propagate error messages safely (will require changes for each CCE)
(c) possibly redesigning MessageResult to use no allocations or at least delegate back to a non-RT thread, but maybe unnecessary.