ddl: support storage class table attributes

## Enhancement

Problem Summary:
Upstream TiDB currently lacks SQL and metadata support for table and partition storage class attributes, so users cannot express storage class intent in DDL or inspect that metadata through schema interfaces.

What would you like to be added:
- `STORAGE_CLASS` syntax for table and partition definitions.
- `ENGINE_ATTRIBUTE` storage-class metadata persistence across create, alter, add partition, and reorganize partition flows.
- `SHOW CREATE TABLE` and `INFORMATION_SCHEMA.TABLES` / `INFORMATION_SCHEMA.PARTITIONS` exposure for storage class metadata.

Why is this needed:
This closes the SQL-layer gap for tiered-storage metadata management so table definitions, partition DDL, and schema introspection stay consistent.

Related PR: #69605.

Start by reviewing related PR #69605, then trace the SQL and metadata paths for table and partition definitions. Done means storage-class attributes work across create, alter, add-partition, and reorganize-partition flows, and appear consistently in SHOW CREATE TABLE and the specified INFORMATION_SCHEMA views.

Written by the indexing model from the issue text.