Improve summary and progress visualization of BR

[Leavrth]

Enhancement

Snapshot restore

1. the snapshot restore summary doesn't show the time consumption of the detail tasks, such as split&scatter region and download&ingest SST.
2. the snapshot restore progress is distorted because the progress length is composed of the number of tables and files. Usually their gap is quite large.

Snapshot backup

1. the snapshot backup summary shows the number of write-CF and default-CF SST files.