[Feature Request] Allow Workers to Submit Output Bindings during execution

#### What problem would the feature you're requesting solve? Please describe.
If a worker function wants to, say, write to a table output binding, and there is a problem with that binding, there is no way to inform the worker function that the table binding is incorrect during execution so that it can take appropriate action, therefore CreateIfNotExists and other patterns are not possible without leveraging direct SDKs, which kind of defeats the point of using outputbinding in the first place.

#### Describe the solution you'd like
Add an RPC call for workers to be able to submit output bindings during invocation and have them immediately evaluated, so that if there is a problem (e.g. table entry already exists), an exception response can be sent to the worker so that it or its downstream function can react accordingly *during* execution.

#### Describe alternatives you've considered
Direct SDK access to Table API/Cosmos/etc., kind of defeats the point of using output bindings though

#### Additional context
https://github.com/Azure/azure-functions-language-worker-protobuf/issues/47

No source files or tests are identified in the issue. Start by reviewing the proposed worker-language protobuf RPC in the linked issue, then trace how the host handles worker invocations and output bindings. Done means workers can submit bindings during execution and receive binding errors during that invocation.

Written by the indexing model from the issue text.