performance: fuse_snapshot very slow

[BohuTANG]

Summary

mysql> select count() from fuse_snapshot('db7861', 't7861');

+---------+
| count() |
+---------+
|    3179 |
+---------+
1 row in set (12 min 2.99 sec)

Task:

• Get all the ss files from the root path with list chore: try to fast read_snapshot #8098
• Change optimize table xx purge to parallel reads

[BohuTANG]

Now the snapshot read is using opendal listand read in parallel, it's fast than before, let's close.