Make Allure result files durable before publishing

[vdvukhzhilov]

• Stage Allure filesystem artifacts (test/container/globals JSON and attachments) as .allure-write-*.tmp in the results directory, sync with fflush / fsync (when available), then rename to the final name so live readers do not see partially written finals.
• On overwrite platforms where rename-over-existing fails (typical Windows), move the old final aside, publish the staged file, then remove the aside backup; if publish fails after the aside step, restore the old final when possible and keep the staged temp with the new payload.
• Incomplete temps (failure before sync) are deleted; fully synced temps are kept if publish fails so the new payload is not lost.

[delatrie]

That should do the job. One thing I would revisit though is the syncCallback parameter of FileSystemResultsWriter. It creates an obscure API: it's not obvious for callers that the callback replaces the default syncing mechanism rather than being called along it.

Do we really need sync override? If yes, having just the overridable syncStreams method should be enough. Otherwise, the syncing method should be private.