rustdoc: Styling regressions from stable to beta

[camelid]

Regression 1

Ayu-only. The summary in the search results is now blue, when it used to be white.

beta (incorrect)

stable (correct)

Regression 2

Ayu-only. The color of impls in Ayu has changed from white to yellow. This may be intentional, but it looked off when I saw it. Note that this happens for all impls, not just foreign impls.

beta (incorrect)

stable (correct)

Regression 3

All themes. Certain auto-trait, foreign, unconditional impls have underlines.

beta (incorrect)

stable (correct)

Regression 4

All themes. The phrase (keyword) next to match in the search results is now red in addition to match itself being red, whereas (keyword) used to be gray.

beta (incorrect)

stable (correct)

Meta

All of the regressions seem to have occurred in beta (1.54.0).

[GuillaumeGomez]

Regression 3 is fixed in #87035.

[GuillaumeGomez]

Sending a fix for the three others.

[GuillaumeGomez]

Regressions 1 and 4 are fixed in #87085.