CAMEL-24392: Fix BacklogTracerRouteAdvice draining WrappedFile streambody (backport 4.22.x)

[davsclaus]

Summary

Backport of #25492 to camel-4.22.x.

• Cache the stream in BacklogTracerRouteAdvice.before() when stream caching is enabled, so the body is converted to a re-readable StreamCache before the tracer reads it
• Prevents SFTP streamDownload bodies from being drained by the backlog tracer

Cherry-picked cleanly from main (947aa5f).

Claude Code on behalf of davsclaus

🤖 Generated with Claude Code

[github-actions]

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[gansheer]

@davsclaus Shouldn't the build run on 4.22 backport like for the 4.18 one?

[davsclaus]

CI likely hasnt been setup for that, check the .github ci files - likely need to add 4.22.x branch somewhere