fix(android): Stop duplicating attachments on native events (JAVA-559) (#5548)

* fix(android): Stop duplicating attachments on native events (JAVA-559)

Scope attachments are synced to the native SDK, so native events already
carry them as envelope items in the outbox. When re-ingesting those
cached envelopes, SentryClient re-applied the scope attachments on top,
sending each attachment twice. Skip re-applying scope attachments for
cached envelopes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* changelog

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Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>