statement summary: update statement summary doc (#6695)

[ti-chi-bot]

This is an automated cherry-pick of #6695

Signed-off-by: ClSlaid cailue@bupt.edu.cn

First-time contributors' checklist

• I've signed Contributor License Agreement that's required for repo owners to accept my contribution.

What is changed, added or deleted? (Required)

Update document of statement summary.
Adding document for the new table statements_summary_evicted.

Which TiDB version(s) do your changes apply to? (Required)

• master (the latest development version)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)

What is the related PR or file link(s)?

• Add statements_summary_evicted table to TiDB
• Add cluster_statements_summary_evicted table to TiDB

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• TomShawn

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[TomShawn]

/merge

[ti-chi-bot]

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

Commit hash: bea0cfd