Optimize placement rules in sql

[Icemap]

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What is changed, added or deleted? (Required)

重构整篇 Placement Rules in SQL 文档，用户反馈结构较乱。

1. 规范用词：

   • 同义的 参数、选项，统一为 参数
   • 同义的 放置规则、放置策略，统一为 放置规则 （与 configure-placement-rules.md 保持一致）
   • 其他不严谨的用词

2. 更改结构：

   • 将 绑定放置规则 中，创建、更新、删除 放置规则的部分单独成章。
   • 高级参数 中，不应放在 示例 下的部分，转为在 放置规则参数参考 一章中描述。

3. 参数解释：

   • 添加了参数的解释，如 SCHEDULE 中的 EVEN/ MAJORITY_IN_PRIMARY 原本无任何解释，SQL 参数亦无。需要相关技术审核，以防出现谬误。
   • 更改了 PRIMARY_REGION / REGIONS 中较晦涩的句法。

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[shawn0915]

@TomShawn 有几点建议，PTAL.

格式：有几处加粗斜体显示不对，建议修正 typo：查询表已绑定放置规则名称, myplacementpolicy 应为 my_policy 其他：工具兼容性， “BR 兼容性” 的页面，并没有“放置规则”相关说明 易用：建议将create table的示例中加入drop table if exists t1;，不然将示例中的语句复制出来测试时还需要再手动删一次表。 补充：建议补充【重置库、表绑定的放置规则】章节，

ALTER DATABASE test PLACEMENT POLICY default;
ALTER TABLE t1 PLACEMENT POLICY default;

[ti-chi-bot]

@Icemap: PR needs rebase.

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[qiancai]

Removed the needs-cherry-pick-release-6.3 label because the v6.3 docs have been archived at https://docs-archive.pingcap.com/zh/tidb/v6.3 and will no longer receive new updates.

[qiancai]

Removed the needs-cherry-pick-release-6.4 label because the v6.4 docs have been archived at https://docs-archive.pingcap.com/zh/tidb/v6.4 and will no longer receive new updates.

[qiancai]

Removed the needs-cherry-pick-release-6.6 label because the v6.6 docs have been archived at https://docs-archive.pingcap.com/zh/tidb/v6.6 and will no longer receive new updates.

[qiancai]

Removed the needs-cherry-pick-release-7.2 label because the v7.2 docs have been archived at https://docs-archive.pingcap.com/zh/tidb/v7.2 and will no longer receive new updates.

[ti-chi-bot[bot]]

@Icemap: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-verify	dc43e54b8f63983649849128bfeb9a52a3c3427b	link	true	/test pull-verify

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