Azure OpenAI: release changelog for beta.3 (#34342)

* Azure OpenAI: relese changelog for beta.3

* Prepare-Release.ps1 run; propagating minor updates

sdk/openai/Azure.AI.OpenAI/CHANGELOG.md

@@ -1,14 +1,16 @@
 # Release History
 
-## 1.0.0-beta.3 (Unreleased)
+## 1.0.0-beta.3 (2023-02-17)
 
 ### Features Added
+- Support for streaming Completions responses, a capability that parallels setting `stream=true` in the REST API, is now available. A new `GetStreamingCompletions` method on `OpenAIClient` provides a response value `StreamingCompletions` type. This, in turn, exposes a collection of `StreamingChoice` objects as an `IAsyncEnumerable` that will update as a streamed response progresses. `StreamingChoice` further exposes an `IAsyncEnumerable` of streaming text elements via a `GetTextStreaming` method. Used together, this facilitates providing faster, live-updating responses for Completions via the convenient `await foreach` pattern.
+- ASP.NET integration via `Microsoft.Extensions.Azure`'s `IAzureClientBuilder` interfaces is available. `OpenAIClient` is now a supported client type for these extension methods.
 
 ### Breaking Changes
+- `CompletionsLogProbability.TokenLogProbability`, available on `Choice` elements of a `Completions` response value's `.Choices` collection when a non-zero `LogProbability` value is provided via `CompletionsOptions`, is now an `IReadOnlyList<float?>` vs. its previous type of `IReadOnlyList<float>`. This nullability addition accomodates circumstances where some tokens produce expected null values in log probability arrays.
 
 ### Bugs Fixed
-
-### Other Changes
+- Setting `CompletionsOptions.Echo` to true while also setting a non-zero `CompletionsOptions.LogProbability` no longer results in a deserialization error during response processing.
 
 ## 1.0.0-beta.2 (2023-02-08)
 ### Bugs Fixed