New placement rule engine

[xhebox]

Enhancement

This is a sub-task of Placement Rules in SQL: #18030. Depends on #26580 and #26581. Once metadata has been finished, we need to add a new middle state to all related DDL jobs to sync rules to PD. Previous, we have already implemented similar code, so the work is more of a migration.

This requires the following subtasks:

• truncate table/partition
• exchange table/partition
• drop db/table/partition
• create db/table/partition
• alter db/table/partition
• flashback/recover table/partition, since metadata is stored in meta, we can revert ddl: handle placement rule cache for drop/truncate/recover/flashback table #20622 and special infoschema treatment for placement rules

[morgo]

I have moved the tasks of this sub-issue to #18030

This was a suggestion to make it easier to see what tasks are unassigned. It makes sense to me, so I am going to close this issue.