Typeless supports interface and abstract

[neuecc]

Fixes #970

[neuecc]

I've found DynamicObjectResolver does not ignore abstract type.
Therefore, the following changes have been made.

- if (ti.IsInterface)
+ if (ti.IsInterface || ti.IsAbstract)

Until now, ContractlessStandardResolver has been able to serialize the abstract class (but not deserialize it).
Therefore, it's a breaking change, but I don't think it was intended to work.

[neuecc]

what reason of test exec failed?

[AArnott]

what reason of test exec failed?

From the failed test step in the PR build:

The active test run was aborted. Reason: Test host process crashed : Process is terminating due to StackOverflowException.

That should presumably be reproducible through a local test run. If not, I can update the Azure Pipeline YAML with some updates from my Library.Template repo that includes collection of crash dump files so you can analyze an AzP test process crash locally on your machine.
Let me know how your investigation goes.

[neuecc]

thanks, I've found stackoverflow.
I'll fix it.

[neuecc]

@AArnott
dddacef
ExpandoObjectFormatter.Serialize causes recurssive get formatter when typeless scenario.
I've inlined serialize method.

and I found TypelessObjectResolver does not use cache.
In addition, I added cache as well.
ccc02ab

[neuecc]

unity build was stalled but other tests completed successfully.