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
This way, we can show the plus and minus buttons on screens, while voice
control will read off actual words "Collapse" and "Expand" instead of reading
"open brace minus close brace" and "open brace plus close brace".
Part of #87059
