Fix error handling propagation

[Chris Gillum (cgillum)]

Resolves #161

For whatever reason, we forgot to fully implement exception propagation in this MSSQL backend for the Durable Task Framework. Fundamentally, the reason this is easy to miss is because the MSSQL provided doesn't serialize history events, but rather manually reads and writes them into structured SQL tables.

In this PR, we implement handling for both ErrorPropagationMode.SerializeExceptions (which we call "legacy") and ErrorPropagationMode.UseFailureDetails (which I'm treating as the new default).

To summarize the changes in this PR, we:

• Make sure to read/write failure details to and from the database as JSON
• Make sure we surface error details in the right way in the public API
• Add new tests or improve existing tests to verify that we flow exception details in expected ways

[Varshitha Bachu (bachuv)]

Looks good to me! Just left a small question.

[aaditya8]

Hi, We are waiting for this fix from so long and upgraded sqlserver libraries and core libraries and started testing with both the modes "ErrorPropagationMode.SerializeExceptions", "ErrorPropagationMode.UseFailureDetails". Please find my observations help me with my use case.

Use Case :

We have one parent orchestration , one sub orchestration under parent orchestration , one task(Activity) under sub orchestration.
I am expecting to propagate the exception occurred in sub orchestration task to both Sub orchestration and Parent orchestration. Below are my findings.

Scenarios :

1. With SerializeExceptions : Inner Exception is always null in Sub Orchestration and Parent Orchestration.
2. With UseFailureDetails : I am able to see the Failure details(Including stack trace) of the Sub Orchestration Activity in Sub Orchestration. Same way i am able to see the failure details of Sub Orchestration in Parent Orchestration but not able to see the Failure details of Sub orchestration activity. Its coming as null.

Could you please help me with this.

[Chris Gillum (cgillum)]

aaditya8 please open a new issue for this and include details such as the kind of exceptions that are being raised. In that new issue, please also share code that shows how you're setting up your TaskHubWorker.