feat(samples): Make Android error buttons identifiable in Sentry (#5722)

Every button on the sample app's Errors tab sent generic, indistinguishable
events (e.g. two buttons both threw "Uncaught Exception from Java." and "Send
Message" sent "Some message."), so there was no way to tell which button
produced which event in Sentry.

Each Errors button now tags its event with sample_action=<button key> (reusing
the existing SentryTraced keys) and uses distinctive text that names the button.
Buttons whose crash carries no message (stack overflow, OOM, native) are still
identifiable via the tag. The native captured message is likewise renamed.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>