[WIP]: add v8.5.0 release notes

[qiancai]

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

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For details, see tips for choosing the affected versions.

• master (the latest development version)
• v8.4 (TiDB 8.4 versions)
• v8.3 (TiDB 8.3 versions)
• v8.2 (TiDB 8.2 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)
• v5.4 (TiDB 5.4 versions)
• v5.3 (TiDB 5.3 versions)

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

• This PR is translated from: [WIP]: add v8.5.0 release notes docs#19336
• Other reference link(s):

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

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[YangKeao]

LGTM

[ti-chi-bot]

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[Frank945946]

Suggested change

	* Schema 缓存内存上限功能成为正式功能（GA），减少了大规模数据场景的内存占用 [#50959](https://github.com/pingcap/tidb/issues/50959) @[tiancaiamao](https://github.com/tiancaiamao) @[wjhuang2016](https://github.com/wjhuang2016) @[gmhdbjd](https://github.com/gmhdbjd) @[tangenta](https://github.com/tangenta) tw@hfxsd <!--1976-->
	* Schema 缓存内存上限功能成为正式功能（GA），可以在集群拥有数十万甚至百万个数据库或表的场景中减少内存的使用。 [#50959](https://github.com/pingcap/tidb/issues/50959) @[tiancaiamao](https://github.com/tiancaiamao) @[wjhuang2016](https://github.com/wjhuang2016) @[gmhdbjd](https://github.com/gmhdbjd) @[tangenta](https://github.com/tangenta) tw@hfxsd <!--1976-->