Google Analytics 4 Upgrade Long Tail

[e0d]

Less urgent and could be split into a separate ticket

• Create a new GA4 property for training.openedx.io
• Create a new GA4 property for sandbox.openedx.org
• Figure out who should have access to the various GA resources and update any relevant docs

Relates to #279

[sarina]

Did we ever put GA4 on either training or sandbox? Should we follow up on this?