Precompile Markdown parsing AND printing

[PallHaraldsson]

Improvement on top of #55715, replacing it, to also precompile printing. And then also fixing parsing and using regression for #55706.

[PallHaraldsson]

[This shouldn't need a full CI, since a trivial tested add-on.]

This is likely the better backport target for 1.11, assuming it only adds to pkgimage (i.e. not the sysimage), not concerned about bloating it, a bit.

This could precompile a bit more for stdout, not just stderr, but unsure how to do that, also likely not a large improvement. It also misses some tags, for images, not as important, maybe easy to add, but I don't want this to hold up releasing 1.11. Can always be added later...

[PallHaraldsson]

Julia support the CommonMark extension: https://www.markdownguide.org/extended-syntax/ but is it the only one, e.g. no R Markdown allowed? The parser will not fail at any extension, just ignore it, so might be ok to include here, for later compatibility?

I was looking into what basic tags to add here, and what more, maybe, I see we likely do not support latest 2024 CommonMark https://spec.commonmark.org/0.31.2/changes.html since I found in the code: https://spec.commonmark.org/0.19/#absolute-uri

[KristofferC]

Note that this will precompile many things for

julia> typeof(devnull)
Base.DevNull

which is not the type that will typically be used when printing things.

[PallHaraldsson]

This is now done.

You can't simply skip devnull, because then it would show, and I'm not sure how to avoid that differently, than I do now.

[PallHaraldsson]

I think ithis is now done for the 1.11 backports. Only question is the precompile I got for Markdown (probably harmless to have here; or skip it): precompile(Tuple{typeof(Base.:(^)), String, Int64})