Support feature tracking and impressions from using the .NET SDK

In DataDog, there's a Feature Flag Tracking dashboard under the Real User Monitoring feature set that has Split.io integrations to track feature flags based on user impressions. However, the current integration only provides tracking for client-side impressions (Javascript).

The current primary usage of feature flags for our organization comes from server-side feature management using the .NET SDK (we are primarily an .NET/C# shop). Being able to send feature flag details and impressions to DataDog from the .NET SDK would be helpful, or else we would have to write our own custom integration.