rustdoc: don't strip <p> from stability notes

[lolbinarycat]

I believe the reason we were doing this before was that write_html_fmt adds a \n after each <p> element.

I have worked around this by making white-space:pre-wrap apply only to the contents of each paragraph, so the inserted whitespace between paragraphs is not included.

Perhaps a better solution would be getting rid of pre-wrap entirely, and instead inserting
events in place of newlines, but that would be a significantly larger change.

fixes #149732

r? @GuillaumeGomez

[rustbot]

Some changes occurred in HTML/CSS/JS.

cc @GuillaumeGomez, @lolbinarycat

[GuillaumeGomez]

Wouldn't it be simpler to replace \n with <br>?

[lolbinarycat]

@GuillaumeGomez do you mean pre-parsing? that wouldn't work bc we disable inline html support for depreciation notes.

honestly i'm tempted to say we should just completely break this over an edition, making it use normal markdown handling and telling people to escape their html tags and use <br> and non-breaking spaces if they want the old behavior. unsure if we would want to do that in addition to or instead of making this change.

[GuillaumeGomez]

Yeah, that would make more sense.

[lolbinarycat]

I think I'll just go ahead and implement that change for EditionFuture, then add a class for the legacy word wrap behavior. Hopefully when edition 2027 is being drafted up someone greps for EditionFuture and finds that? I guess we could add the maybe-future-edition label to the issue to make it easier to find?

Some might find it odd to make edition changes this far in advance, but I think it's a good idea in order to avoid crunch time.

[GuillaumeGomez]

I think so too. Although I wonder if we really need to put it behind an edition change. Might be worth discussing with the team, don't you think? Eventually that will allow you to have less work to do. 😉