📜 Description

When merging tombstone and Native SDK events, we assume the message from the Native SDK. However, in most cases, this property will be empty from the Native SDK, whereas we explicitly construct a message from the tombstone that closely matches what debuggerd would print in logcat. This PR uses the tombstone message if the native envelope doesn't provide one.

💡 Motivation and Context

Better crash information.

💚 How did you test it?

📝 Checklist

• I added GH Issue ID & Linear ID
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.