Use proper semantic HTML for inline text formatting

[barklund]

Feature Description

Since #1323 all inline text formatting in a text field is done using <span> and inline style properties.

This should be changed to proper semantic HMTL elements where applicable - e.g. going from the current:

<span style="font-weight: 800">Hello</span>
<span style="text-decoration: underline">world!</span>

To:

<strong style="font-weight: 800">Hello</strong>
<em>world!</em>

Thus using semantic elements where possible (for bold font-weights, italic and underline) and keep spans where not (for non-bold font weights, text color and letter spacing).

This however requires moving away from the current draft-js-export-html dependency to a custom DraftJS-to-HTML converter (and of course vice-versa).

---

Do not alter or remove anything below. The following sections will be managed by moderators only.

Acceptance Criteria

QA Instructions

[o-fernandez]

@barklund do you think this is important for Beta? Stable?

[swissspidy]

Related: #5326

[BrittanyIRL]

@miina this feels like a prometheus thing? Not really sure why it got relabeled pea pod (but that was like 14 months ago so....)