feat(csharp): add withRawResponse() support

[devin-ai-integration]

Description

Refs: Slack request from @tjb9dc

Adds the ability to access raw HTTP response data (status code, headers) when making API calls in the C# SDK, similar to the TypeScript implementation.

Link to Devin run: https://app.devin.ai/sessions/10231e3101304c52917326b69a8fdab9
Requested by: [email protected] (@tjb9dc)

Changes Made

• Added RawResponse<T> template class with Body, StatusCode, and Headers properties
• Created RawSubPackageClientGenerator and RawRootClientGenerator for generating raw client classes
• Added WithRawResponse property to client classes that returns the raw client instance
• Modified HttpEndpointGenerator to generate raw response methods when generateRawResponse: true
• Registered RawResponse in AsIs.ts and added type references in generation-info.ts
• Added changelog entry for version 2.10.0
• Updated README.md generator (if applicable) - N/A

Updates Since Last Revision

• Fixed compile errors: replaced this.System.NotSupportedException with this.Types.BaseException for unsupported endpoint types
• Fixed generateRawResponse parameter propagation through EndpointGenerator.ts
• Added changelog entry to versions.yml (version 2.10.0 - minor bump required for feat type)
• Fixed HEAD endpoint handling: HEAD requests now correctly return RawResponse<HttpResponseHeaders> instead of RawResponse<object> (caught by http-head seed test)

Testing

• Unit tests added/updated
• Manual testing completed (lint checks pass locally)
• All CI checks passing

Human Review Checklist

⚠️ Important items for reviewer:

1. Seed tests not updated - No seed test fixtures were updated to validate the generated C# code compiles. CI passed using existing fixtures.

2. Streaming endpoints throw BaseException - Raw response wrapper is not supported for streaming, streamParameter, and bytes endpoints. These will throw BaseException at runtime. Is this acceptable?

3. Pagination not supported - Raw response methods use unpaged endpoint signature, so paginated endpoints may not work correctly with WithRawResponse.

4. Template design - Review RawResponse.Template.cs - uses int for StatusCode (not HttpStatusCode enum) and HttpResponseHeaders for headers.

[devin-ai-integration]

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