[WIP]: add v8.5.0 release notes

[qiancai]

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• v8.3 (TiDB 8.3 versions)
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[YangKeao]

LGTM

[lilin90]

@hfxsd These are comments on highlight and new features. I'll continue with reviewing improvements and bug fixes soon later.

[lilin90]

@hfxsd PTAL. Thanks!