ci: Upgrade non-dist Linux testers from ubuntu:16.04 to 22.04
The main goal of updating to 22.04 is to get away from `llvm.allow-old-toolchain`.
A side benefit is that they can also use the system `cmake` instead of building one.
rustdoc: remove incorrect CSS selector `.impl-items table td`
Fixes#100994
This selector was added in c7312fbae4. The bug can be seen at <https://doc.rust-lang.org/1.27.0/alloc/slice/trait.SliceIndex.html#foreign-impls>.
This rule was added to help with a `<table>` that was used for displaying the function signature [src] lockup. That lockup was changed in 34bd2b845b to use flexbox instead, leaving this selector unused (at least, for its original purpose).
rustdoc: omit start/end tags for empty item description blocks
Related to #100952
This is definitely not a complete solution, but it does shrink keysyms/index.html on smithay from 620K to 516K.
Resolves all of issue #93240
Reproduces a similar change as #99086, but with improvements
In particular, this PR inlcludes:
* redesigning the crate-search selector so the background color matches its surroundings
* decrease the font of the dropdown menu to a reaonable size
* add a hover effect
* make the color of the arrow theme-dependent, using a surrounding div, with :after pseudo-element
that can then be transformed using CSS filters to approximate the desired color
* fix the text "in" to match the title font
* remove the "for xyz" in the "Results for xyz in [All crates]" title when
searching for search term "xyz"; you can already see what you're searching for
as it's typed in the search bar!
* in line with #99086, handle super-long crate names appropriately without a long <select>
element escaping the screen area; the improvement is that we also keep the title
within a single line now; uses some flex layout shenanigans...
* the margins / paddings are adjusted so the selected label of the <select> fits within
the rest of that title nicely; also some inconsistency in the way that Firefox renders
a <select> with "appearance: none" (roughly 4px more padding left and right of the text
than e.g. Chrome) is worked around, and it now produces a result that looks (essentially)
identical to Chrome
* the color of the help menu and settings menu border in light theme is made to match with
the color of the corresponding buttons, like they do (match) in the ayu theme
* the casing of "All crates" changes to "all crates"
* the new tests from #99086 are temporarily disabled, until they can be adapted later
rustdoc: improve scroll locking in the rustdoc mobile sidebars
This PR prevents the main content area from scrolling while the mobile sidebar is open on documentation pages (porting the scroll locking behavior from the source sidebar to the regular sidebar), and also fixes some bad behavior where opening a "mobile" sidebar, and growing the viewport so that the "desktop" mode without scroll locking is activated, could potentially leave the page stuck.
This does not affect the behavior on larger screens. Only small ones, where the sidebar covers up the main content.
Split out from #98772
This commit ports the scroll locking behavior from the source sidebar to the
regular sidebar, and also fixes some bad behavior where opening a "mobile"
sidebar, and growing the viewport so that the "desktop" mode without scroll
locking is activated, could potentially leave the page stuck.
This does not affect the behavior on larger screens. Only small ones, where
the sidebar covers up the main content.
rustdoc: improve click behavior of the source code mobile full-screen "sidebar"
On desktop, if you open the source code sidebar, it stays open even when you move from page to page. It used to do the same thing on mobile, but I think that's stupid. Since the file list fills the entire screen on mobile, and you can't really do anything with the currently selected file other than dismiss the "sidebar" to look at it, it's safe to assume that anybody who clicks a file in that list probably wants the list to go away so they can see it.
Split out separately from #98772
rustdoc: make source sidebar toggle a real button
This fixes tab focus, so that you can open and close the sidebar from keyboard.
This should cause no visible change in appearance at all. The only way you'd know anything different is if you tried to use keyboard controls to open the source code file navigation sidebar.
Separated out from #98772
rustdoc: use <details> tag for the source code sidebar
This fixes the extremely poor accessibility of the old system, making it possible to navigate the sidebar by keyboard, and also implicitly gives the sidebar items the correct ARIA roles.
Split out separately from #98772
On desktop, if you open the source code sidebar, it stays open even when you
move from page to page. It used to do the same thing on mobile, but I think
that's stupid. Since the file list fills the entire screen on mobile, and you
can't really do anything with the currently selected file other than dismiss
the "sidebar" to look at it, it's safe to assume that anybody who clicks a
file in that list probably wants the list to go away so they can see it.
This fixes the extremely poor accessibility of the old system, making it
possible to navigate the sidebar by keyboard, and also implicitly gives the
sidebar items the correct ARIA roles.
