Drop markdown headings to solve dup headings

[guardrex]

Fixes #19846

This is temporary until we can lay hands on version-by-file. At that point, I'll revert back to markdown-style headings.

cc: @Rick-Anderson @scottaddie @wadepickett ... The HTML tag headings approach bypasses the build system, but I did need to apply different tag ids. This approach provides stable text across sections without a visible version to readers. I'll just do this temporarily until hopefully 🤞 we get version-by-file and then revert back to plain markdown headings.

This is the only Blazor topic with this problem right now, so it's trivial to revert later. I'll see how Blazor WASM security topics play out when I work the content for RC1. It might not be that bad. There might not be many changes, so whole-topic versioning might not be required. If so, I don't expect new dup heading issues.

[serpent5]

@guardrex Is this the same problem I saw earlier in the year in #17491? Can you point me to more information re how version-by-file will work (if you get it)?

[guardrex]

Scott will let us know ... track on ...

#19831 (comment)

Yes ... there are several pain points with whole topic versioning. We think version by file will fix the dup headings problem, the cross-link problem, and the dup alt text problem. It probably will be nicer for just performing general updates when you know what version you need to apply a change to. We'll just open the file for that version instead of having to search for content under a moniker range within a multi-version file.

[guardrex]

We kind'a knew from the start that there would be some problems ... it's very clear that moniker ranges were never designed to be used for whole topic versioning. I think it's clear at this point that they either want us to version little bits of content (paragraphs, code snippets, etc.) or use version by file. However, massive churn across versions, especially minor releases, makes the topic insane to maintain flipping in and out of versions. The Kestrel topic was probably the worst back when it had like four versions and was flipping in and out of different moniker ranges every few paragraphs. 😨 It cleaned up very well when we went to whole-topic, but now all of these new problems have come up.

CORRECTION ... Actually, 🤔 ... I think it was three versions ... BUT ... there were version ranges across two of the three AND single version sections. It was flipping in and out of moniker ranges every few paragraphs tho.

[serpent5]

Ok, understood. Thanks for the information - I've subscribed to the linked issue to see how things progress.