[Feature/SSH] SSH session-related operations are not thread-safe

[koNinja]

Summary

SSH operations are not thread-safe.
When multiple Cloud Filter API callbacks are invoked concurrently, the process does not work correctly.

Expected Behavior

• Multiple placeholder fetch requests are processed correctly at the same time.

Actual Behavior

• If a fetch request occurs while a fetch operation is already in progress, an error occurs and it never works properly again.

[koNinja]

Currently, the issue is avoided by having the synchronization provider handle mutual exclusion.