[Python] Support for untyped Json

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.