[Feature Flag] API to track evaluations #4008
Description
Problem Statement
This request is agnostic of integrations.
tl;dr: Add new API: AddFeatureFlag to SDK
Develop docs: https://develop.sentry.dev/sdk/expected-features/#feature-flags
Solution Brainstorm
This will unblock Unity. We'll be adding support for Firebase, Unity Cloud Services and other providers in the future.
But is also relevant for .NET, for the current supported providers (e.g: LaunchDarkly) but also, Azure App Configuration: