*: Add resource management topic and split docs

[nolouch]

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[ti-chi-bot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
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[songrijie]

Suggested change

	- `lightning`：使用 [TiDB Lightning](/tidb-lightning/tidb-lightning-overview.md) 执行导入任务。同时支持 TiDB Lightning 的物理和逻辑导入模式。
	- `lightning`：使用 [TiDB Lightning](/tidb-lightning/tidb-lightning-overview.md) 和 [`IMPORT INTO`](/sql-statements/sql-statement-import-into.md) 执行导入任务。同时支持 TiDB Lightning 的物理和逻辑导入模式。

[nolouch]

import into 现在还不支持

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[glorv]

LGTM

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