Rollup merge of #118756 - jyn514:colors, r=estebank

use bold magenta instead of bold white for highlighting

according to a poll of gay people in my phone, purple is the most popular color to use for highlighting

| color      | percentage |
| ---------- | ---------- |
| bold white | 6%         |
| blue       | 14%        |
| cyan       | 26%        |
| purple     | 37%        |
| magenta    | 17%        |

unfortunately, purple is not supported by 16-color terminals, which rustc apparently wants to support for some reason.
until we require support for full 256-color terms (e.g. by doing the same feature detection as we currently do for urls), we can't use it.

instead, i have collapsed the purple votes into magenta on the theory that they're close, and also because magenta is pretty.

before:
![image](https://github.com/rust-lang/rust/assets/23638587/9a89eee2-8b89-422e-8554-812827bb2a23)

after:
![image](https://github.com/rust-lang/rust/assets/23638587/5bf3a917-8a20-4afd-af3e-f9491d0d57f5)

other colors for comparison:
blue: ![image](https://github.com/rust-lang/rust/assets/23638587/6f199c7b-d598-4009-8ffc-6b7b1d0d1f8c)
cyan: ![image](https://github.com/rust-lang/rust/assets/23638587/a77e4fe3-563e-4aa5-ae92-745bb67287d1)
purple: ![image](https://github.com/rust-lang/rust/assets/23638587/ffe603fb-d811-4106-95a9-4dd4c955924c)
magenta without bolding: ![image](https://github.com/rust-lang/rust/assets/23638587/cf927e5f-8b25-4dc2-b8e7-32905a11a459)

r? ``@estebank``

Author: matthiaskrgr