Quay should by default enable flags of "nested repo","initial create user" and "create public repository on push"

Description:

Now in Quay 3.6.0, when Quay Customers want to use new features of "nested repository", " Create public repository on push", "Create initial user with API", they need to add the following flags in config.yaml manually,  to improve customers experience, pls add these configs with default value as true.

FEATURE_EXTENDED_REPOSITORY_NAMES: true
CREATE_REPOSITORY_ON_PUSH_PUBLIC: true
FEATURE_USER_INITIALIZE: true