feat: Add slimrpc support for .NET (C#)

[janosSarusiKis]

Description

Resolves:
#1265

Type of Change

• Bugfix
• New Feature
• Breaking Change
• Refactor
• Documentation
• Other (please describe)

Checklist

• I have read the contributing guidelines
• Existing issues have been referenced (where applicable)
• I have verified this change is not present in other open pull requests
• Functionality is documented
• All code style checks pass
• New code contribution is covered by automated tests
• All new and existing tests pass

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf CI / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Mar 18, 2026, 1:22 PM

[codecov]

Codecov Report

❌ Patch coverage is 97.04348% with 17 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
data-plane/slimrpc-compiler/src/csharp.rs	98.06%	11 Missing ⚠️
...mrpc-compiler/src/bin/protoc-gen-slimrpc-csharp.rs	0.00%	6 Missing ⚠️

📢 Thoughts on this report? Let us know!

[msardara]

LGTM, with nits ✅

I get this warning when trying to build:

/Users/msardara/repos/slim/data-plane/bindings/dotnet/Slim.Examples.SlimRpc/Program.cs(143,52): warning CS1998: This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread. [/Users/msardara/repos/slim/data-plane/bindings/dotnet/Slim.Examples.SlimRpc/Slim.Examples.SlimRpc.csproj]

Maybe we can add something like #pragma warning disable CS1998