fix(emotion): add separate namespace for menu app

[nytai]

SUMMARY

Adds emotion cache to the menu "app" so that styles do not collide with other other apps. The cache allows specifying a namespace for the emotion styles that is seperate from the default namespace, used by other "apps" on the same page.

More info on the issue here: emotion-js/emotion#2210

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

before:

after:

TEST PLAN

• run npm run build
• see proper menu styling on the sqllab/dashboard/explore pages.

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Merging #14362 (f3a497d) into master (8767798) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master   #14362      +/-   ##
==========================================
- Coverage   77.14%   77.13%   -0.01%     
==========================================
  Files         954      954              
  Lines       48148    48148              
  Branches     5987     5986       -1     
==========================================
- Hits        37143    37140       -3     
- Misses      10808    10811       +3     
  Partials      197      197              

Flag	Coverage Δ
javascript	72.01% <0.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
superset-frontend/src/views/menu.tsx	0.00% <0.00%> (ø)
...et-frontend/src/dashboard/components/SaveModal.tsx	45.45% <0.00%> (-1.72%)	⬇️
...erset-frontend/src/SqlLab/components/SqlEditor.jsx	54.62% <0.00%> (ø)
...src/explore/components/controls/VizTypeControl.jsx	81.48% <0.00%> (+1.82%)	⬆️

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