optimize execution of general DDL

[D3Hunter]

Enhancement

we have optimize create table using fast-create, but there are scenarios that we might create a lot of database, or run many DDLs like add/modify column in the maintenance window.
so we want to optimize execution of general DDL, and in a unified way

• ddl: sync schema version using watch, notify sessions on owner node by job id #53217
• add index on type for tidb_ddl_job to make some query faster
• move job dependency calculation into memory, to avoid the slower SQL
• run general DDLs with multiple workers
• notify the session which is not on DDL owner node when owner finished handling by RPC or other way
• ddl: manage job lifecycle in worker #53747
• other refactors
  • ddl: decouple job scheduler from 'ddl' and make it run/exit as owner changes #53548