Report app start type via app context

[markushi]

Problem Statement

Similar to Cocoa, we want to provide the app start type property for transactions via the contexts: contexts.app.start_type

Solution Brainstorm

Cocoa Implementation

Example Cocoa Transaction

[markushi]

Docs around this topic: https://docs.sentry.io/platforms/apple/performance/instrumentation/automatic-instrumentation/#prewarmed-app-start-tracing