docs: Improve documentation around "Status" of `CaptureFeedback`

### Summary

Improve `sentry-docs` and C# XML Documentation Comments of overloads of public `CaptureFeedback` with `out CaptureFeedbackResult` in parameter list.

### Remarks

In #4613 we changed `CaptureFeedback` to also return "status"/"result" information of the invoked API.
But getsentry/sentry-unity#2715 shows that there can be a confusion about what `CaptureFeedbackResult.Success` means.
We can improve our documentation and XML comments to be a bit more clear that this means successful validation of the input, and that no event processors has prevented the envelope from being handed off to the `IBackgroundWorker` nor being sent via the `ITransport`.