v8.5.6: refresh TopSQL docs and screenshots (#21431)

[ti-chi-bot]

This is an automated cherry-pick of #21431

What is changed, added or deleted? (Required)

• Refresh dashboard/top-sql.md to match the current pingcap/tidb-dashboard master behavior.
• Update the Top SQL doc to cover Top 5/20/100, CPU/Network/Logical IO ordering, TiKV By Query / By Table / By DB / By Region, and the enable/disable behavior for TiKV network IO collection.
• Re-shoot and replace the Top SQL screenshots with the current UI, including the TiKV Order By Network and Order By Logical IO views.
• Add two new screenshots to explicitly show the Order By dropdown and the Top SQL settings drawer for enabling TiKV Network IO collection.

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

• master (the latest development version)
• v9.0 (TiDB 9.0 versions)
• v8.5 (TiDB 8.5 versions)
• v8.1 (TiDB 8.1 versions)
• v7.5 (TiDB 7.5 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)
• v6.1 (TiDB 6.1 versions)
• v5.4 (TiDB 5.4 versions)

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

• This PR is translated from:
• Other reference link(s):
  • https://github.com/pingcap/tidb-dashboard/tree/master

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

[yibin87]

LGTM

[ti-chi-bot]

@yibin87: adding LGTM is restricted to approvers and reviewers in OWNERS files.

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In response to this:

LGTM

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[qiancai]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qiancai

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