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

[sophschneider]

after #9913 is completed we need to

### Tasks
- [ ] https://github.com/Shopify/polaris/issues/10189
- [ ] https://github.com/Shopify/polaris/issues/10191
- [ ] https://github.com/Shopify/polaris/issues/10190
- [ ] https://github.com/Shopify/polaris/issues/10192
- [ ] https://github.com/Shopify/polaris/issues/10193
- [ ] https://github.com/Shopify/polaris/issues/10194
- [ ] https://github.com/Shopify/polaris/pull/10239
- [ ] https://github.com/Shopify/polaris/pull/10241
- [ ] https://github.com/Shopify/polaris/pull/10243
- [ ] https://github.com/Shopify/polaris/pull/10242
- [ ] https://github.com/Shopify/polaris/pull/10244
- [ ] https://github.com/Shopify/polaris/issues/10254
- [x] 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