Slightly better error handling in AsynchronousMetrics

Why it matters

This feature addresses the issue where ClickHouse would fail to start or encounter errors if the /sys/block directory is present but inaccessible. By improving error handling, the server can now continue starting and operate without monitoring block devices, enhancing stability and robustness in such environments.

How to use it

No explicit user action is required. The improved error handling is applied automatically when ClickHouse detects the /sys/block directory but cannot access it; the server will proceed without enabling block device monitoring.