v8.5.7: support logging session connect attrs to slow query log (#21468)

[ti-chi-bot]

This is an automated cherry-pick of #21468

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What is changed, added or deleted? (Required)

This PR updates docs according to pingcap/tidb#66617:

• Add Session_connect_attrs (json) to the schema examples of INFORMATION_SCHEMA.SLOW_QUERY and INFORMATION_SCHEMA.CLUSTER_SLOW_QUERY.
• Add the system variable doc for performance_schema_session_connect_attrs_size (default/range/-1 behavior/truncation/1 MiB hard limit note).
• Add status variable docs:
  • Performance_schema_session_connect_attrs_longest_seen
  • Performance_schema_session_connect_attrs_lost
• Update SESSION_CONNECT_ATTRS doc with size limit and truncation behavior.

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• v9.0 (TiDB 9.0 versions)
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• v6.5 (TiDB 6.5 versions)
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• v5.4 (TiDB 5.4 versions)

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

• This PR is translated from: docs: support logging session connect attrs to slow query log  docs#22547
  • *: support logging session connect attrs to slow query log tidb#66617
• Other reference link(s):

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

[ti-chi-bot]

@hfxsd This PR has conflicts, I have hold it.
Please resolve them or ask others to resolve them, then comment /unhold to remove the hold label.

[ti-chi-bot]

@ti-chi-bot: ## If you want to know how to resolve it, please read the guide in TiDB Dev Guide.

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[yibin87]

LGTM

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

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LGTM

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[lilin90]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lilin90

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch master: #21751.
But this PR has conflicts, please resolve them!