Donut chart UX updates

[michaelnesen]

What does this implement/fix?

https://github.com/Shopify/core-issues/issues/74649

This PR adds some new UX updates to the DonutChart:

• Makes thickness of donut arcs smaller when container height is small
• Makes the donut chart take up more space in the container:

Before	After

• Adjusts spacing for legend with values

Does this close any currently open issues?

https://github.com/Shopify/core-issues/issues/74649

What do the changes look like?

Storybook link

https://6062ad4a2d14cd0021539c1b-brxtckilvd.chromatic.com/

Before merging

• [x] Check your changes on a variety of browsers and devices.

• [x] Update the Changelog's Unreleased section with your changes.

• [x] Update relevant documentation, tests, and Storybook.

• [x] Make sure you're exporting any new shared Components, Types and Utilities from the top level index file of the package

[github-actions[bot]]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
polaris-viz-core-cjs	61.19 KB (+0.08% 🔺)	1.3 s (+0.08% 🔺)	1.1 s (+1.72% 🔺)	2.3 s
polaris-viz-cjs	215.29 KB (+0.03% 🔺)	4.4 s (+0.03% 🔺)	2.3 s (+14.51% 🔺)	6.6 s
polaris-viz-esm	176.19 KB (+0.01% 🔺)	3.6 s (+0.01% 🔺)	1.3 s (-0.58% 🔽)	4.9 s
polaris-viz-css	4.72 KB (-0.03% 🔽)	95 ms (-0.03% 🔽)	229 ms (-46.97% 🔽)	324 ms
polaris-viz-esnext	181.84 KB (+0.01% 🔺)	3.7 s (+0.01% 🔺)	1.3 s (-5.3% 🔽)	4.9 s