DataCollection phase 2: propagate to native (Android/Cocoa)

[jamescrosswell]

Part of #5420. Phase 2 — consumer migration (.NET-specific).

Propagate DataCollection to the native layers:

• src/Sentry/Platforms/Android/SentrySdk.cs:63 and src/Sentry/Platforms/Cocoa/SentrySdk.cs:37 currently forward options.SendDefaultPii to the Java/Cocoa SDKs.
• Until sentry-java / sentry-cocoa implement the DataCollection spec: down-convert the resolved config to the native sendDefaultPii boolean conservatively (only true when the resolved config is at least as permissive as legacy-true).
• Forward FrameContextLines / StackFrameVariables to native equivalents where they exist (context lines are populated by the native layers, not managed code).
• Track native-SDK parity as follow-ups; revisit this mapping when sentry-java / sentry-cocoa ship their own dataCollection.

[linear-code]

NET-771