Implement rustdoc-scrape-examples

[mejrs]

This implements rustdoc-scrape-examples for the docs that we host ourselves (not the docs.rs ones - I figure it's best to see how this goes first). Example.

This also:

• Implements a full feature that incorporates all additional features
• Resolves #2053
• Fixes a link I messed up on the __call__ example in the guide
• Fixes some links to anyhow and eyre's documentation
• Adds cargo aliases for rendering docs
• Renders and hosts internal documentation: Example

Note that this creates a dead link to "decorator" in the sidebar. This should be fixed by rust-lang/rust#92146

I also haven't touched the makefile yet - should I?

[davidhewitt]

Nice, this looks great to me!

Few various tidy-up suggestions etc.

I also haven't touched the makefile yet - should I?

If you agree we should move towards cargo aliases (with "xtask" like in #2067 for more complex scripts), we can work to kill off the Makefile? If so, then don't worry about updating it here.

[davidhewitt]

Should this become cargo pyo3_doc ?

[mejrs]

Actually, would you be OK with removing this step? Building docs is also tested in guide.yml.

[davidhewitt]

Hmmm, I do think there's value in checking the docs build on all each of windows, Linux and macos. Probably doesn't need to be run for each Python variant. Could make it 3.10-only?

[davidhewitt]

Looks good to me! Feel free to merge this as-is. I'll let you decide whether to change the docs build CI step here or in a follow up PR.

[mejrs]

Looks good to me! Feel free to merge this as-is. I'll let you decide whether to change the docs build CI step here or in a follow up PR.

I'm not sure I even want to change it now, seeing as it seems to work fine as it is (I'm guessing the rustdocflags don't get passed for some reason?).

Moving it to guide.yml and rendering docs for each possible combination of cfgs would require rebuilding pyo3 for each of those (?).

[davidhewitt]

Mmm ok, let's keep as-is for now!