sql-statements: update claims on optimizer/explain compatibility

[morgo]

What is changed, added or deleted? (Required)

TiDB does not support EXPLAIN FORMAT=tree. It comes from MySQL 8.0, so it had not previously been documented (our official claim = 5.7), but users might not know this. So it helps to include it here.

Note: I've updated this to cover optimizer switch compatibility as well. In pingcap/tidb#29040 we determined that optimizer_switch should be read_only for now.

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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)
• v5.2 (TiDB 5.2 versions)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)
• v4.0 (TiDB 4.0 versions)
• v3.1 (TiDB 3.1 versions)
• v3.0 (TiDB 3.0 versions)
• v2.1 (TiDB 2.1 versions)

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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
• dveeden

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[yudongusa]

LGTM

[ti-chi-bot]

@yudongusa: 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.

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[morgo]

@TomShawn PTAL, thanks!

[TomShawn]

/merge

[ti-chi-bot]

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

Commit hash: d44f95f

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #7295.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #7296.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #7297.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #7298.