Fixes some accidental styling issues introduced in #19242

Almost done. Just need to fix up some stories.

Changes made

• Updated styles
• Added support for className prop so that we can override the styles as needed
• Removed the aria-label in favor of injecting the main text directly

Notes

• This feels like a case where the changes in the previous PR were actually correct overall, but something with our MUI+Tailwind setup created conflicting styles, and we accidentally introduced an underline style that shouldn't be there
• Removed the Aria label because I've realized in the past year that Aria is really easy to misuse, and it's best just to do things with the base HTML features as much as possible. There's a risk that the old code had compliance issues with certain types of screen readers (even though it worked fine when I did manual testing back in 2023). These changes hopefully remove those risks completely