Add changelogs for M.E.AI projects (#5577)

Author: stephentoub

src/Libraries/Microsoft.Extensions.AI.Abstractions/CHANGELOG.md

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+# Release History
+
+## 9.0.0-preview.9.24525.1
+
+- Lowered the required version of System.Text.Json to 8.0.5 when targeting net8.0 or older.
+- Annotated `FunctionCallContent.Exception` and `FunctionResultContent.Exception` as `[JsonIgnore]`, such that they're ignored when serializing instances with `JsonSerializer`. The corresponding constructors accepting an `Exception` were removed.
+- Annotated `ChatCompletion.Message` as `[JsonIgnore]`, such that it's ignored when serializing instances with `JsonSerializer`.
+- Added the `FunctionCallContent.CreateFromParsedArguments` method.
+- Added the `AdditionalPropertiesDictionary.TryGetValue<T>` method.
+- Added the `StreamingChatCompletionUpdate.ModelId` property and removed the `AIContent.ModelId` property.
+- Renamed the `GenerateAsync` extension method on `IEmbeddingGenerator<,>` to `GenerateEmbeddingsAsync` and updated it to return `Embedding<T>` rather than `GeneratedEmbeddings`.
+- Added `GenerateAndZipAsync` and `GenerateEmbeddingVectorAsync` extension methods for `IEmbeddingGenerator<,>`.
+- Added the `EmbeddingGeneratorOptions.Dimensions` property.
+- Added the `ChatOptions.TopK` property.
+- Normalized `null` inputs in `TextContent` to be empty strings.
+
+## 9.0.0-preview.9.24507.7
+
+Initial Preview

src/Libraries/Microsoft.Extensions.AI.AzureAIInference/CHANGELOG.md

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+# Release History
+
+## 9.0.0-preview.9.24525.1
+
+- Lowered the required version of System.Text.Json to 8.0.5 when targeting net8.0 or older.
+- Updated to use Azure.AI.Inference 1.0.0-beta.2.
+- Added `AzureAIInferenceEmbeddingGenerator` and corresponding `AsEmbeddingGenerator` extension method.
+- Improved handling of assistant messages that include both text and function call content.
+
+## 9.0.0-preview.9.24507.7
+
+Initial Preview

src/Libraries/Microsoft.Extensions.AI.Ollama/CHANGELOG.md

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+# Release History
+
+## 9.0.0-preview.9.24525.1
+
+- Lowered the required version of System.Text.Json to 8.0.5 when targeting net8.0 or older.
+- Added additional constructors to `OllamaChatClient` and `OllamaEmbeddingGenerator` that accept `string` endpoints, in addition to the existing ones accepting `Uri` endpoints.
+
+## 9.0.0-preview.9.24507.7
+
+Initial Preview

src/Libraries/Microsoft.Extensions.AI.OpenAI/CHANGELOG.md

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+# Release History
+
+## 9.0.0-preview.9.24525.1
+
+- Lowered the required version of System.Text.Json to 8.0.5 when targeting net8.0 or older.
+- Improved handling of system messages that include multiple content items.
+- Improved handling of assistant messages that include both text and function call content.
+- Fixed handling of streaming updates containing empty payloads.
+
+## 9.0.0-preview.9.24507.7
+
+Initial Preview

src/Libraries/Microsoft.Extensions.AI/CHANGELOG.md

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+# Release History
+
+## 9.0.0-preview.9.24525.1
+
+- Added new `AIJsonUtilities` and `AIJsonSchemaCreateOptions` classes.
+- Made `AIFunctionFactory.Create` safe for use with Native AOT.
+- Simplified the set of `AIFunctionFactory.Create` overloads.
+- Changed the default for `FunctionInvokingChatClient.ConcurrentInvocation` from `true` to `false`.
+- Improved the readability of JSON generated as part of logging.
+- Fixed handling of generated JSON schema names when using arrays or generic types.
+- Improved `CachingChatClient`'s coalescing of streaming updates, including reduced memory allocation and enhanced metadata propagation.
+- Updated `OpenTelemetryChatClient` and `OpenTelemetryEmbeddingGenerator` to conform to the latest 1.28.0 draft specification of the Semantic Conventions for Generative AI systems.
+- Improved `CompleteAsync<T>`'s structured output support to handle primitive types, enums, and arrays.
+
+## 9.0.0-preview.9.24507.7
+
+Initial Preview