fix merged functions and constants as values in html docs generator

[metruzanca]

This closes #4214

Do we want the functions/constants removed from the main content area? I've kept them for now.

Here's a preview:

Thanks @giacomocavalieri for the moral support in discord as usual.

[metruzanca]

Not sure why snapshot_kind: text was removed when doing cargo insta review. Let me know if this is an issue and I can amend. (first time using the tool)

[GearsDatapacks]

I think it's just a field from an older version of the tool which is not present any more.

[lpil]

Great, thank you! Could you sort them into alphabetical order too please

Do we want the functions/constants removed from the main content area? I've kept them for now.

Could you merge it all into one please, and also alphabetically sorted 🙏

[metruzanca]

Could you merge it all into one please, and also alphabetically sorted

Alright in that case, moving away from this naive solution to a more complete one. I think I'll combine DocsFunction and Constant into DocsValue. That way in generate_html I can sort before the flat_map and as a result cleanup the now messy template. Using options for the extra fields functions have (seems like askama templates have good support for this).

Have only played around with rust thus far, let me know if this sounds rusty enough.

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I'll probably code up an attempt of this tomorrow morning (my tz: est)