Applies_to: Change default lifecycle to "Available" rather than "Generally Available"

Today when not specifying a lifecycle in applies_to, we assume "ga" as default value. In some cases, this could be misleading because "ga" is also a way to not show the lifecycle on the badge, making it easier to read;

With this change, I'm proposing to change the default meaning of no lifecycle specified.
- The badge will keep showing no lifecycle
- The popover will show "Available" instead of "Generally Available"
- With this new default, don't show support information in the popover. For example, the example below would simply be a non-expandable line that indicates "Available since 9.2".

This will avoid conflating these simpler uses of applies_to with actual support/production information whereas in many cases when not specifying it, it is to actually not show the lifecycle (as it may be communicated by a bigger section or page item)

cc @shainaraskas following docs-eng sync