Plugin request for Buf Schema Registry: Grpc.Net.Client

## Mandatory I believe the source code is here: https://chromium.googlesource.com/external/github.com/grpc/grpc/+/HEAD/src/csharp/Grpc.Tools/ ## Optional **Does the plugin have a valid semver version?** Yes, see here: https://www.nuget.org/packages/Grpc.Tools/ **Does the plugin have a dependency on another plugin?** I don't believe so. **Does the output of this plugin depend on any other external libraries?** I don't believe so. ## Motivation There's a [grpc/csharp](https://buf.build/grpc/csharp?version=v1.78.0) plugin already, but it generates code that uses `Grpc.Core`, which [is deprecated](https://grpc.io/blog/grpc-csharp-future/). There's an [approach that uses dotnet tooling](https://learn.microsoft.com/en-us/aspnet/core/grpc/basics?view=aspnetcore-10.0#c-tooling-support-for-proto-files), but it'd be awesome from my perspective if Buf supported this as well.