Enable VisualEditor as a Beta Feature on Commons

Also enable it on the Creator and Institution local namespaces, alongside
the content namespaces (for Commons, this is just NS_MAIN) and the default
set (NS_USER, NS_FILE, NS_HELP, and NS_CATEGORY).

Bug: 65067
Change-Id: Iaa51c03c29e9b5526ceff53b2c5524b16286e4c9
Merge "Enable VisualEditor as a Beta Feature on Commons"