refactor: adopt primer design system ui components

[setchy]

Closes: #1541

Adopts the excellent GitHub Primer Design System Component Library - https://primer.style/components to replace our custom components and provide a level-up on user experience and visual consistency.

This PR, though sizeable, focuses on replacing the following components

• Icons
• Buttons
• Layout via Stack

I have also replaced most tests to use data-testid and getByTestId so that they're more resilient to UI changes

Items found during testing that should be resolved

• Horizontal scroll bar showing on notification animation (mark as read, etc)
• Different uses of colors (tailwind vs design token), eg: green color
• position of repository title tooltip gets cut off

[bmulholland]

I have also replaced most tests to use data-testid and getByTestId so that they're more resilient to UI changes

Lovely, nice touch.

[setchy]

Appreciate the kind words @afonsojramos and the feedback on some visual inconsistencies. I'll address them shortly 👨‍💻

[setchy]

However, I've found a couple of visual issues:

Apologies this took a while to get back to. Items 1, 2 and 3 have been addressed

I think we're getting quite close to this being merged. 6.x.x milestone perhaps?

[afonsojramos]

@setchy do you want some help in the replacement of the sxs?

[setchy]

@setchy do you want some help in the replacement of the sxs?

Absolutely! Always welcome a friendly hand.

I haven't attempted to remove the style components used with primer components... I'm not sure how feasible that will be, but if possible I'm keen

[afonsojramos]

Seems like it is not possible 😅 We need to override the component's defaults... Oh well 🤷 It's annoying, but isn't much of a problem.

[setchy]

Thanks for taking a look 🙏

[setchy]

@bmulholland @afonsojramos - I've resolved all merge conflicts and done some final refactoring to our tailwind colors.

I think I'm ready for final review from you both if you have some time 🙏

There is one niggling issue remaining whereby the user-selected theme is not correctly loading on startup...

[setchy]

There is one niggling issue remaining whereby the user-selected theme is not correctly loading on startup...

This is now resolved. Left a few TODO comments for future us to clean up some of the legacy theming code