Support incubator features preview in zilla release docker image

[jfallows]

Describe the desired outcome from the user's perspective
As a developer, I want to be able to try out zilla incubator features using the official zilla release, rather than having to build a local develop-SNAPSHOT docker image first.

Acceptance criteria

• incubator feature implementations are included in zilla release docker image
• incubator features are disabled by default in zilla release docker image
• incubator features can be enabled when executing zilla commands
• incubator features are no longer enabled by default for local builds
• new incubator features are marked incubator by default until explicitly moved out of incubator

Additional context
None

Tasks

• Allow each extensibility point to indicate if it is an incubator feature, true by default, overridden as needed
• Engine discovers all extensibility points, but ignores incubator features if not enabled
• EngineConfiguration to enable incubator features, false by default
• ZillaCommand support to enable incubator features, including incubator commands
• ZillaStartCommand configures Engine to enable to disable incubator features
• ZillaMetricsCommand configures Engine to enable to disable incubator features
• Unify incubator and release jammy Dockerfile, build alpine image on actual release
• Update zilla-examples for incubator features to use latest docker image and enable incubator features