`OnUnhandledReducerError` in client SDKs

Name not yet decided. Semantics basically locked in by BitCraft needs. Specifically:

When receiving a TransactionUpdate for a known reducer with status Failed or OutOfEnergy, check if there are any callbacks registered on that reducer. If none are registered, invoke the OnUnhandledReducerError with a ReducerEventContext containing the failed reducer and with an Error/Exception object that contains the error message.

Callbacks are of the type FnMut(&module_bindings::ReducerEventContext, sdk::Error).

For the OutOfEnergy case, the passed Error should be distinguishable as meaning out of energy.

Callbacks are registered and removed directly on the DbContext. In Rust, this means the trait DbContext has methods on_unhandled_reducer_error(&self, callback) -> OnUnhandledReducerErrorCallbackId and remove_on_unhandled_reducer_error(&self, callback_id: OnUnhandledReducerErrorCallbackId).

This is high priority in C#, as BitCraft needs this functionality. It is significantly lower priority in Rust and TypeScript.

Start by locating the client SDK implementations of TransactionUpdate handling and DbContext callback registration, especially the Rust DbContext trait and the C# and TypeScript equivalents. Trace Failed and OutOfEnergy updates, then verify that unhandled reducer errors invoke the callback with ReducerEventContext and distinguishable error information across the intended SDKs.