MWPW-162452 OST promocode fix

[3ch023]

Resolve https://jira.corp.adobe.com/browse/MWPW-162452

Fix OST opening without promo override value.
Remove Gallery from mas - we should use the Milo one.
move mas-commerce-service into a Studio.
add commerce env switch (needed to test promocode in action)

what's missing: open ost with stage commerce env, will add it later

Test URLs:

• Before: https://main--mas--adobecom.hlx.live/studio.html
• After: https://MWPW-162452--mas--adobecom.hlx.live/studio.html

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Commits

• 311148a ✅ (latest)
• 9e13ffd ✅

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	Page	Scores	Audits	Google
📱	/studio.html
🖥️	/studio.html