Adds implementation of the `info` function.
Added support for blobs in the function integration test stuff.
Simplified usage of integration test classes by removing the account name parameter.
### Function implementation
Added implementation of `agent_events` function and some basic tests.
Fixed several issues encountered in `TestOperations`.
### Additional JsonConverter
The existing Python code for `agent_events` figures out which class to use only based upon the shape of the input, without a discriminator. I have added an additional `JsonConverter` named `SubclassConverter<T>` which will pick a subclass of `T` to deserialize into based upon what properties exist in the JSON.
### Enum helpers
Converted some enum helpers to extension methods to make them a bit more readable.
Add support for function tests and the ability to run them against either real Azure Storage or the Azurite emulator.
See follow-up PR #2032 for actual usage.
