Draft: [#462] Improve autodoc behavior for nested entrypoints

Description

Current autodocs are not ideal due to several reasons, and this MR is used to correct some of them:

• Add function(s) to traverse builded documents to gather some data from them
• Add some connection between inner and outer entrypoints (in for of a link, mention etc.)
• Add inner entrypoints to list of all entrypoints

Related issue(s)

Resolves #462 (closed)

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• Tests (see short guidelines)

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  • I updated changelog files of all affected packages released to Hackage if my changes are externally visible.

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