[Box] Add border width support

[aveline]

WHY are these changes introduced?

Part of #7601

WHAT is this pull request doing?

• Adds border with support only with this PR as further exploration is needed to implement border color
• Sets the initial border width to --p-border-width-1 which works currently as all the existing shorthand border properties use that width. Setting to initial doesn't work as the browser initial is medium which overrides the shorthand width.

Playground code

      <AlphaStack fullWidth>
        <Box
          paddingInlineEnd="10"
          paddingInlineStart="10"
          border="divider"
          borderWidth="1"
        >
          test
        </Box>
        <Box border="dark" borderWidth="3">
          test
        </Box>
        <Box border="dark" borderBlockStartWidth="3">
          test
        </Box>
        <Box border="dark" borderBlockEndWidth="3">
          test
        </Box>
        <Box border="dark" borderInlineStartWidth="3">
          test
        </Box>
        <Box border="dark" borderInlineEndWidth="3">
          test
        </Box>
        <Box border="dark" borderBlockEndWidth="2">
          test
        </Box>
        <Box
          border="divider"
          borderBlockEndColor="border"
          paddingInlineEnd="10"
          paddingInlineStart="10"
        >
          test
        </Box>
      </AlphaStack>

[github-actions]

size-limit report 📦

Path	Size
polaris-react-cjs	209.63 KB (+0.04% 🔺)
polaris-react-esm	136.1 KB (+0.08% 🔺)
polaris-react-esnext	191.26 KB (+0.08% 🔺)
polaris-react-css	41.37 KB (+0.11% 🔺)

[kyledurand]

Nice clean up 👍

[laurkim]

Nice! 💯
Small nit, the get-props script should probably be run with this pr to pick up the new props in the style guide.