Add .NET Feature Management support

[nascosto]

Is your feature request related to a problem? Please describe.
.NET now provides a feature management library: https://learn.microsoft.com/en-us/azure/azure-app-configuration/feature-management-dotnet-reference?pivots=stable-version. The built in providers are fairly simple, but they provide interfaces that allow extension. We'd like to take advantage of this library since Microsoft provides it as a standard.

Describe the solution you'd like
Implementing an IFeatureDefinitionProvider as well as other interfaces they provide for LaunchDarkly would allow us to take advantage of the built in framework while still getting the power of LaunchDarkly.

Describe alternatives you've considered
N/A

Additional context
N/A