[Python] Support for untyped Json

[andrueastman]

Similar to https://github.com/microsoft/kiota/pull/4095 we need to add support for untyped content in request/response payloads.

In summary, we need to

• [ ] Add UntypedNode base type in the abstractions library (see https://github.com/microsoft/kiota-abstractions-dotnet/pull/177)
• [ ] Add derived types of UntypedNode to represent object, array and primitive types in the abstractions (see https://github.com/microsoft/kiota-abstractions-dotnet/pull/177)
• [ ] Update the getObjectValue method in the json serialization library to handle scenarios of untyped content (see https://github.com/microsoft/kiota-serialization-json-dotnet/pull/198)
• [ ] Remove the call to RemoveUntypedNodePropertyValues in the refiner so that untyped properties are not stripped out.
• [ ] Add tests in the generator.
• [ ] Ensure the "apisguru::apis.guru" integration test is passing.