Align subscription APIs with Commonalities 0.5.0

[akoshunyadi]

Problem description
Commonalities 0.5.0 contains an updated template for subscriptions https://github.com/camaraproject/Commonalities/blob/main/artifacts/camara-cloudevents/event-subscription-template.yaml

Possible evolution
Align all 3 subscription APIs with the template

• device-roaming-status-subscriptions
• device-reachability-status-subscriptions
• connected-network-type-subscriptions

Alternative solution

Additional context

[bigludo7]

Discussed with @akoshunyadi : Connected Network Type Subscriptions did not describe initialEvent & subscriptionMaxEvents attributes in the yaml - we should add these.

[bigludo7]

@sachinvodafone Are you able to take care of this one ? or do you need some help?
cc: @akoshunyadi