New nugets (Abstractions, Connectors.AI.OpenAI); add AAD auth, Azure ChatGPT, text+chat streaming (#420)

### Motivation and Context

New features:
* AAD auth for Azure OpenAI
* Azure ChatGPT
* Completion streaming
* Chat streaming
* log probs

### Description

* Split kernel core nuget in 3 nugets and add dependency on Azure OpenAI
SDK:
* MS.SK.Abstractions: interfaces and common classes, ideally no business
logic
  * MS.SK: SK runtime, depends on SK.Abstractions
* MS.SK.Connectors.AI.OpenAI: OpenAI/Azure OpenAI code, depends on
SK.Abstractions and Azure OpenAI SDK
* Rewrote TextCompletion, ChatCompletion, EmbeddingGeneration clients to
use Azure OpenAI SDK
* Deleted unused code. The old OpenAI client is still in use only for
DALL-E2

Note: custom retry logic doesn't work with Azure OpenAI SDK. The SDK
already retries internally, using a different approach.

Nugets:
* Microsoft.SemanticKernel.0.12.0.nupkg
* **Microsoft.SemanticKernel.Abstractions.0.12.0.nupkg**
* **Microsoft.SemanticKernel.Connectors.AI.OpenAI.0.12.0.nupkg**
* Microsoft.SemanticKernel.Connectors.Memory.Qdrant.0.12.0.nupkg
* Microsoft.SemanticKernel.Connectors.Memory.Sqlite.0.12.0.nupkg
* Microsoft.SemanticKernel.Skills.MsGraph.0.12.0.nupkg
* Microsoft.SemanticKernel.Skills.Document.0.12.0.nupkg
* Microsoft.SemanticKernel.Skills.OpenAPI.0.12.0.nupkg
* Microsoft.SemanticKernel.Skills.Web.0.12.0.nupkg

python/DEV_SETUP.md

@@ -98,7 +98,7 @@ You should be able to run the example under the [tests](tests) folder.
 ## Pipeline checks
 
 To run the same checks that run during the GitHub Action build, you can use
-this command, from the [python](/python) folder:
+this command, from the `python` folder:
 
     poetry run pre-commit run -c .conf/.pre-commit-config.yaml -a