Refrain from overwriting the span status for unfinished spans

[markushi]

Problem Statement

As discussed in getsentry/sentry-java#1690 unfinished spans should be sent, but their status should not be set to deadline_exceeded.

Tasks

Beta Give feedback

1. Refrain from overwriting the span status for unfinished spans sentry-java#2730
   Platform: Android Platform: Java +2
   
2. Refrain from overwriting the span status for unfinished spans sentry-cocoa#3060
   Breaking-change Platform: Cocoa +2
3. Refrain from overwriting the span status for unfinished spans sentry-react-native#3216
   Platform: React-Native +1
4. Refrain from overwriting the span status for unfinished spans sentry-dart#1481
   Breaking-change Platform: Dart performance +3
   
5. Include unfinished spans in transactions sentry-dotnet#1182
   Feature Platform: .NET Product: Tracing +3
   
6. Unity (same as .NET)

From the Relay Issue:

Relay will no longer drop transactions that contain Spans without end timestamp
In this approach, the SDKs can remove the logic of handling unfinished spans. Relay now will be free to take the best approach to the problem:

Relay will add the transaction’s timestamp to the Span and the status deadline_exceeded, to indicate this span didn't complete during the transaction.

Relevant Relay PR: getsentry/relay#1690
Note: for older self-hosted installations this can break transactions

Solution Brainstorm

Don't overwrite the span status.

[markushi]

After taking a closer look at the relay changes leaving the status untouched is not enough, we also need to set no end time on the span.
Relay will only set the status to deadline_exceeded if no end time is provided. Along the way it will also set an end time.