[ti-chi-bot]

This is an automated cherry-pick of #21747

What is changed, added or deleted? (Required)

• Clarify DM foreign key replication constraints when foreign_key_checks=1.
• Document that DM supports static one-to-one table routing for multi-worker foreign key causality, and still rejects route rules that map multiple source tables in the task to the same target table in this mode.
• Document that compact and multiple-rows are not supported when foreign_key_checks=1.
• Document hot configuration update restrictions when foreign_key_checks=1 and worker-count > 1.
• Add a schema correctness note recommending standard foreign key definitions before migration.

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

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions.

• 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)

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

• This PR is translated from: master: clarify DM foreign key support for one-to-one routing docs#23153
• Other reference link(s):
  • dm: make FK relation builder route-aware tiflow#12654
  • dm: support FK causality for one-to-one routes tiflow#12675
  • dm: reject FK causality hot config updates tiflow#12703
  • v8.5.6: dm experimentally supports foreign key docs#22616

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

[lilin90]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lilin90

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