add support for createIndexStmt and dropIndexStmt

[deadspacewii]

fix create index indexName on tableName and drop index on DDL statment

[deadspacewii]

This PR addresses the changes requested in #843

[dveeden]

Would it be possible to add some tests?

[deadspacewii]

Would it be possible to add some tests?
it's hard to repeat this situation, but i can show you：

type MyEventHandler struct {
canal.DummyEventHandler
}

func (h *MyEventHandler) OnDDL(header *replication.EventHeader, nextPos mysql.Position, queryEvent *replication.QueryEvent) error {
fmt.Println("query: ", string(queryEvent.Query))
fmt.Println("schame: ", len(string(queryEvent.Schema)))
fmt.Println("type: ", header.EventType)
return nil
}

cfg := canal.NewDefaultConfig()
c, err := canal.NewCanal(cfg)
if err != nil {
log.Fatal(err)
}

c.SetEventHandler(&MyEventHandler{})
c.Run()

i use this code to get ddl sql,but when i use alter table test add index index_name (id), this queryevent can be fetch by canal, but if i use create index index_name on test (id),
canal can't get the queryevent and return. i see the source code, find sync.parseStmt method do not match *ast.DropIndexStmt and *ast.CreateIndexStmt(because the parse of
tidb config the create index and drop index as *ast.CreateIndexStmt and *ast.DropIndexStmt). finally, it cause nothing to output when i use create index and drop index

[deadspacewii]

Would it be possible to add some tests?
I have create three tests，you can see and run

[lance6716]

thanks for your PR. please check my comment and apply it for the DROP INDEX test cases

[lance6716]

and here, you can use require.Equal(t, db, rdb) and require.Equal(t, baseTable, rtable)

[deadspacewii]

I have apply require package to test