Support for Feedback Events #3605

Originally posted by @jamescrosswell in #3604

The .NET SDK is still implementing User Feedback using a USER_REPORT_ENVELOPE which means feedback has to be associated with exception events (an eventid is required in the envelope).

Since then a new Feedback Events format has been introduced that allows User Feedback to be sent independently of exceptions. The .NET SDK. should also support Feedback Events.

This involved a new function: CaptureFeedback.

This function is the base functionality needed to allow capturing user feedback while including tags, replay_id, trace_id, etc.
It's part of the 'new user feedback' product (getsentry/sentry#64671) that was shipped for Web. That included a built-in widget, that allows screenshot attachment, and under the hood relies on this new function that deprecates the old CaptureUserFeedback which required an event_id. The new function optionally takes a related event_id and will contain relevant context stand alone.

This means a new envelope format for feedback was introduced.
The new Feedback product architecture has thoroughly documented by @aliu39 here:

• https://develop.sentry.dev/application/feedback-architecture/

This new function will allow outgoing feedbacks to be tied to Session Replay, which is currently Open Beta and we're working on GA:

• [Epic] Mobile Replay: GA sentry#74441

The develop docs have not been added yet, but the ticket with details about it is here:

• SDK docs for User Feedback v2 develop#1206

Relates to:

• Add new captureFeedback API to RN SDK sentry-react-native#3859
• [Android] New User Feedback sentry-java#3599
• Add function to capture user feedback sentry-go#842
• Image upload option during user feedback sentry-dart#1593
• Support captureFeedback sentry-dart#2230
• Add screenshot to SentryFeedbackWidget sentry-dart#2369
• Rename sendFeedback to captureFeedback & enhance it sentry-javascript#10953
• [User Feedback] - Issue Trace Timeline sentry#68481 - trace_id allows the product to show all related telemetry collected during that trace