Add TIDB_PLACEMENT_POLICY_NAME and TIDB_DIRECT_PLACEMENT to information_schema.schemata

[morgo]

Currently the information_schema tables for tables and partitions have columns for placement options. This is useful because it can be used to find which objects are making use of a placement policy (assuming you want to drop it, but it's in use).

However, the information_schema table for schemas (schemata) does not have these columns. It makes sense to add this, since it is a schema level attribute as well.

[sylzd]

/assign