`captureMessage` on Android using `attachStacktrace=true` does not send the stacktrace

[marandaneto]

The JS SDK appends the stack trace to a top-level property instead of the threads interface.
It works on iOS because the event is sent as it is.
It fails on Android because of the round trip serialization, since this property does not exist on Android, it's lost.

• Android V6 keeps the unknown fields, which would solve the problem (Still alpha tho).
• The JS SDK could adapt it to use the threads interface (Gonna be done on V7, See the issue).
• The RN SDK could process the event and move the top-level property within the threads interface.

The 3rd option right now seems faster/easier.

[marandaneto]

We've decided to go either with upgrading the Android SDK to v6 or JS SDK to v7, the one that comes first.