added epoch history to log backup files

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: 3pointer, BornChanger

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/pingcap/kvproto/blob/master/OWNERS)~~ [3pointer,BornChanger] - ~~[proto/OWNERS](https://github.com/pingcap/kvproto/blob/master/proto/OWNERS)~~ [BornChanger] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2024-09-23 03:50:30.047819737 +0000 UTC m=+1451499.788243677: :ballot_box_with_check: agreed by 3pointer.
• 2024-09-23 08:06:43.280922988 +0000 UTC m=+1466873.021346926: :ballot_box_with_check: agreed by BornChanger.