[Bug] a lot of files in unsequence folder after old data migration

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/iotdb/issues) and found nothing similar.

### Version

Centos 7.4
0.13.4

### Describe the bug and provide the minimal reproduce step

After migrating data from another iotdb instance to the new one, there are a lot of files in unsequence folder, and the total file size is about 11G, meanwhile, the query performance is very poor for some query sql, which takes about 80+ seconds to finish the query.

### What did you expect to see?

the file size in unsequence folder decrease after run MERGE command in CLI and the query cost should be under 1s.

### What did you see instead?

nothing happen after running the MERGE command.

### Anything else?

_No response_

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!

Comienza reproduciendo la migración desde la otra instancia de IoTDB y, después, ejecuta MERGE en la CLI mientras monitorizas la carpeta unsequence y el tiempo de las consultas. Se considera terminado cuando disminuyan los archivos unsequence y las consultas afectadas se completen en menos de un segundo.

Escrito por el modelo de indexación a partir del texto del issue.