feat(legacy-preset-big-number): use emotion styling

[rusackas]

💔 Breaking Changes

🏆 Enhancements
Adding emotion styling, pulling from Superset theme, particularly for typographic purposes in Big Number plugin. This also removes the CSS file, and puts ALL the styling INSIDE the component where it's exported. Emotion includes SASS out of the box, so I've condensed things a bit accordingly.

This also adds a ThemeProvider to the storybook, so the plugins work/look right there.

Before screenshots:

After screenshots:

📜 Documentation

🐛 Bug Fix

🏠 Internal

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🔍 Inspect: https://vercel.com/superset/superset-ui/1lha6vut3
✅ Preview: https://superset-ui-git-fork-preset-io-big-number-typography.superset.now.sh

[codecov]

Codecov Report

Merging #455 into master will decrease coverage by 0.10%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #455      +/-   ##
==========================================
- Coverage   22.72%   22.62%   -0.11%     
==========================================
  Files         276      281       +5     
  Lines        6670     6696      +26     
  Branches      644      648       +4     
==========================================
- Hits         1516     1515       -1     
- Misses       5115     5142      +27     
  Partials       39       39              

Impacted Files	Coverage Δ
...reset-chart-big-number/src/BigNumber/BigNumber.tsx	0.00% <0.00%> (ø)
plugins/legacy-plugin-chart-table/src/index.ts	0.00% <0.00%> (ø)
plugins/legacy-plugin-chart-iframe/src/index.js	0.00% <0.00%> (ø)
plugins/legacy-plugin-chart-heatmap/src/index.js	0.00% <0.00%> (ø)
plugins/legacy-plugin-chart-horizon/src/index.js	0.00% <0.00%> (ø)
plugins/legacy-plugin-chart-map-box/src/index.js	0.00% <0.00%> (ø)
packages/superset-ui-query/src/buildQueryObject.ts	100.00% <0.00%> (ø)
plugins/legacy-plugin-chart-histogram/src/index.js	0.00% <0.00%> (ø)
...kages/superset-ui-query/src/types/QueryFormData.ts	100.00% <0.00%> (ø)
...ns/legacy-plugin-chart-force-directed/src/index.js	0.00% <0.00%> (ø)
... and 8 more

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[ktmud]

Just noted that the font family for big number is not the same as the default font. LGTM if this is intentional.

[kristw]

LGTM. Same question with @ktmud

[rusackas]

Font change is intentional, bringing it inline with the rest of Incubator-Superset's UI. Other viz pugins will follow suit, changing the fonts for axes, tooltips, whatever. Eventually we'll do the same for colors, border radii, and all the other little bits and baubles that come from the theme. This will be a long tail, but this PR show the pattern.