Handle storefront domains with schemes

[kieran-osgood-shopify]

Summary

• normalize React Native sample storefront domains before building Storefront API URLs
• pass the normalized storefront domain into Checkout Kit accelerated checkout config
• normalize storefront domain values during sample config sync

Validation

• ./scripts/test_setup_storefront_env
• cd platforms/react-native && pnpm test sample/src/tests/storefrontUrl.test.ts --runInBand
• /opt/dev/bin/dev rn lint sample
• Built the React Native iOS sample in Release for the booted iPhone Air simulator with a temporary https:// storefront domain value, installed via agent-device, and verified the Catalog screen renders products instead of the catalog network error