Fix react-native preview only ui

[benoitdion]

Issue

After the typescript migration (#6448) a couple regressions were introduced.

• Default port for server ui was no longer getting set properly
• preview only ui failed on initial render (onDeviceUI: false fails with 5.1.0.alpha.28 (React Native stopped working post alpha.24 until .28) #6545)

What I did

Fixed the above issues, see individual commits for more details.

How to test

• Run the storybook for react-native with onDeviceUI true and false. Switch between stories using the web ui.

[vercel]

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Latest deployment for this branch: https://monorepo-git-react-native-bugs.storybook.now.sh

[codecov]

Codecov Report

Merging #6549 into next will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##             next    #6549      +/-   ##
==========================================
- Coverage   40.77%   40.76%   -0.01%     
==========================================
  Files         616      616              
  Lines        8529     8531       +2     
  Branches      595      596       +1     
==========================================
  Hits         3478     3478              
- Misses       4959     4961       +2     
  Partials       92       92

Impacted Files	Coverage Δ
...-native/src/preview/components/StoryView/index.tsx	0% <0%> (ø)	⬆️
app/react-native/src/preview/index.tsx	0% <0%> (ø)	⬆️

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