[Epic] Globally remove all conditional se23 logic from polaris-react

[sophschneider]

after #9913 is completed we need to

Tasks

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1. [AppProvider] Consolidate se23 logic and styles #10189
   8 of 8
   #gsd:36579 Priority: High +2
   
2. [CI] Remove pre se23 CI checks (CI and a11y/vrt) and remove experimental name from new checks #10191
   4 of 4
   #gsd:36579 +1
   
3. [Storybook] Remove the se23 and shadow bevel toggle #10190
   4 of 4
   #gsd:36579 Priority: High +2
   
4. [Utilities] Consolidate se23 logic and styles #10192
   1 of 1
   #gsd:36579 Priority: High +2
   
5. [Styles] Consolidate se23 styles in polaris-react/src/styles #10193
   #gsd:36579 Priority: High +2
   
6. [ShadowBevel] Clean up shadow bevel mix in opt out properties #10194
   2 of 2
   #gsd:36579 +1
   
7. Consolidate the rest of se23 scss styles #10239
   #gsd:36579 🤖Skip Changelog +2
   
8. Consolidate se23 in the rest of stories #10241
   #gsd:36579 +1
   
9. [CI][Tests] Consolidate se23 tests #10243
   +0
   
10. [Storybook] Consolidate se23 feature toggles #10242
    🤖Skip Changelog +1
    
11. Consolidate the rest of se23 jsx logic #10244
    #gsd:36579 🤖Skip Changelog +2
    
12. [Styles] Consolidate remaining se23 scss logic #10254
    3 of 3
    #gsd:36579 +1
    
13. Do a final code search for se23, polarisSummerEditions2023, polarisSummerEditions2023ShadowBevelOptOut etc. to make sure all conditional code is removed

Note

We can remove $se23ShadowBevelOptOut but not $se23 since a lot of our consuming repos still use the classname and we don't want to affect their styles.

Sources:

• se23 class name used in many consuming repos internally: https://grokt.shopify.io/results?q=Polaris-Summer-Editions-2023
• shadow bevel class name only in polaris: https://grokt.shopify.io/results?q=Polaris-SE23-Shadow-Bevel-Opt-Out

[sophschneider]

We can resume this work once #10423 ships :D