Decrease baseline sizing and spacing in admin

[yesenia-perezcruz]

Default sizing (of text and space) in the admin feels too large and airy

it also does not scale well on low quality monitors where you need to command - several times for the UI to be usable.

• What can we do to adjust the base size and scale so that the UI feels more dense? #4543
  

• What can we do to adjust the size and scale so that it works better (scales better) for low quality monitors?

[alex-page]

• The base font-size is set to font-size: 62.5%; which turns into 10px. This causes poor scaling and a bunch of odd rem values. This PR shipped to fix the issue then got reverted.
• We could use the clamp property in CSS to better style the font-sizes responsively. There are also techniques to scale font-sizes based off browser width.
• Our breakpoints in polaris-react and shopify/web could use some love and centralisation

[ouellettejordan]

There seems to be some bespoke spacing issues on both the Analytics page and Finances pages. Their headers sit higher than all the other pages...

[alex-page]

@ouellettejordan is this maybe because the buttons don't exist on those pages? I wonder if the height of the area changes without them, moving the title text. This shouldn't be the case but just a quick thought/observation.

[ouellettejordan]

Possibly. But needs to be fixed regardless.

[sarahill]

Closing in favor of https://github.com/Shopify/web/issues/52575

We are still investigating other Density improvements and will open another issue for those.