Re-org snapshot for disk table

**Is your feature request related to a problem? Please describe.**
disk-based table

**Describe the solution you'd like**
Now the disk-table snapshot is not used and not necessary. We already have data persist in disk.
Can remove the disk_table_snapshot. But we have to be careful not to break the original snapshot-related features.

Look for disk_table_snapshot in the codebase, likely in storage or snapshot modules. Understand how disk-based tables persist data and how snapshots are used elsewhere to avoid breaking existing functionality. Test after removal to ensure snapshot-related features still work.

Written by the indexing model from the issue text.