[cherry-pick] backup: more detailed TiKV error message(tidb#27567)

[YuJuncen]

cherry-picking tidb#27567

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What problem does this PR solve?

Problem Summary:

The error information when meeting unknown TiKV storage error is too abstract...

What is changed and how it works?

What's Changed:
Added more details to the error.

How it Works:
So we can get more detailed information.

Check List

Tests

• (almost) No code

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• 3pointer
• kennytm

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[YuJuncen]

/run-integration-tests

[fengou1]

/LGTM

[ti-chi-bot]

@fengou1: Thanks for your review. The bot only counts approvals from reviewers and higher roles in list, but you're still welcome to leave your comments.

In response to this:

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[YuJuncen]

/run-integration-tests

[YuJuncen]

/merge

[ti-chi-bot]

@YuJuncen: /merge in this pull request requires 2 approval(s).

In response to this:

/merge

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[kennytm]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: caba877