binlog.schemaVersion is 0 for flaskback cluster, and unlock tables when last table doesn't exist

[D3Hunter]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

right now binlog.schemaVersion is used by CDC to decide when or whether to run the DDL, and binlog.schemaVersion might be 0 when the DDL is skipped due to if not exist, if exist and alter table cache/no cache but table is already in the expect state

but for below cases, binlog.schemaVersion is also 0. as CDC don't sync below types of DDL right now, will mark this issue as moderate

binlog info are not set for flaskback cluster，so binlog.schemaVersion is always 0

tidb/pkg/ddl/cluster.go

Lines 834 to 836 in bb9096c

	job.State = model.JobStateDone
	job.SchemaState = model.StatePublic
	return updateSchemaVersion(jobCtx, job)

for unlock table when last table doesn't exist, the final binlog.schemaVersion is also 0

tidb/pkg/ddl/table_lock.go

Lines 179 to 184 in bb9096c

	if infoschema.ErrDatabaseNotExists.Equal(err) || infoschema.ErrTableNotExists.Equal(err) {
	// The table maybe has been dropped. just ignore this err and go on.
	args.IndexOfUnlock++
	job.FillArgs(args)
	return ver, nil
	}

tidb/pkg/ddl/table_lock.go

Lines 234 to 237 in bb9096c

	ver, err = unlockTables(jobCtx, job, args)
	if args.IndexOfUnlock == len(args.UnlockTables) {
	job.FinishTableJob(model.JobStateDone, model.StateNone, ver, nil)
	}

2. What did you expect to see? (Required)

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

master