Update file_storage to write state to subdirectory

[jefchien]

Description of the issue

The logfile plugin's cleanupStateFolder() globs the state directory (logs/state/*) and deletes any file it cannot parse as its expected two-line offset format. When the journald receiver uses the file_storage extension to persist state in the same directory, the BoltDB files end up being deleted by the state directory cleanup.

Description of changes

Moves the file_storage directory to logs/state/otel to prevent this conflict. Sets the Compaction.Directory to match the storage directory for consistency.

License

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Tests

Tested on EC2 with both logfile and journald configured. The cleanup is non-deterministic, but is possible if the journald receiver is delayed during startup.

  {
    "agent": {
      "debug": true
    },
    "logs": {
      "logs_collected": {
        "files": {
          "collect_list": [
            {
              "file_path": "/var/log/messages",
              "log_group_name": "/test/v1-logs"
            }
          ]
        },
        "journald": {
          "collect_list": [
            {
              "log_group_name": "/test/journald",
              "units": ["sshd"]
            }
          ]
        }
      }
    }
  }

Before

$ ls -la /opt/aws/amazon-cloudwatch-agent/logs/state/
total 20
drwxr-xr-x. 2 root root    42 Jul  2 19:50 .
drwxr-xr-x. 3 root root    90 Jul  2 19:50 ..
-rw-------. 1 root root 32768 Jul  2 19:50 receiver_journald_journald_0

After

$ sudo find /opt/aws/amazon-cloudwatch-agent/logs/state/ -ls
 41944463   0 drwxr-xr-x   3 root root   18 Jul  2 20:07 /opt/aws/amazon-cloudwatch-agent/logs/state/
   491122   0 drwxr-x---   2 root root   42 Jul  2 20:07 /opt/aws/amazon-cloudwatch-agent/logs/state/otel
   671148  20 -rw-------   1 root root 32768 Jul  2 20:07 /opt/aws/amazon-cloudwatch-agent/logs/state/otel/receiver_journald_journald_0

Requirements

Before commiting your code, please do the following steps.

1. Run make fmt and make fmt-sh
2. Run make lint

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Integration Tests

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