br: update restore checkpoint information

[Leavrth]

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  br: migrate pitr id map to the system table mysql.tidb_pitr_id_map tidb#55871
  br: migrate restore checkpoint data to the downstream cluster temporary database tidb#56075

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Timeline:

• 2024-09-25 09:24:17.623886254 +0000 UTC m=+1644327.364310177: ☑️ agreed by 3pointer.
• 2024-09-26 03:12:47.596720029 +0000 UTC m=+1708437.337143968: ☑️ agreed by Oreoxmt.

[qiancai]

“快照备份路径（等于日志恢复的起始时间点 start-ts）”这是什么意思呢

[Leavrth]

比如一个 PITR 恢复命令：

./br restore point --full-backup-storage "local:///tmp/backups-1/full" -s "local:///tmp/backups-1/log"

这相当于基于快照备份 "local:///tmp/backups-1/full"，然后做日志恢复。那么 "local:///tmp/backups-1/log" 恢复区间起始 start-ts 就是快照备份的 backup ts。

我们调整快照备份路径，就相当于调整了快照备份的 backup ts，也相当于调整了日志恢复的起始 start-ts。