Add an only.flavor key to Zarf components

[Racer159]

Is your feature request related to a problem? Please describe.

As Ezra I want the ability to specify "flavors" of Zarf packages and select between them on zarf package create so that I can swap chunks of things like images and valuesFiles without the need to have an entirely separate copy of a Zarf package definition.

Describe the solution you'd like

• Given I have a Zarf package definition
• And that definition has components that specify only.flavor
• When I run zarf package create --flavor my-flavor
• Then Zarf will include all components that match that flavor or have an empty flavor string
• And When I run zarf package create without a flavor
• Then Zarf will include only components that have an empty flavor string

Describe alternatives you've considered

We could have higher order keys like imageSets or have other extensions but this adds complexity without taking advantage of a lot of the base Zarf primitive manipulation that can be done through composability.

Additional context

This initial ask came from a desire to swap images to have a hardened and an upstream version of the same underlying package to help with package development and testing.

[jeff-mccoy]

Here's an example we worked through for Istio 1.19 where there would be an ironbank and upstream flavor:

kind: ZarfPackageConfig
metadata:
  name: uds-capabilities-istio
  description: "UDS Istio Capability"
  url: https://istio.io/latest/
  version: 1.19.0

components:
  - name: istio-controlplane
    import:
      path: common
    only:
      flavor: upstream
    images:
      - "docker.io/istio/pilot:1.19.0"
      - "docker.io/istio/proxyv2:1.19.0"

  - name: istio-controlplane
    import:
      path: common
    charts:
      - name: istiod
        valuesFiles:
          - "values/ironbank.yaml"
    only:
      flavor: ironbank
    images:
      - "registry1.dso.mil/ironbank/opensource/istio/pilot:1.19.0"
      - "registry1.dso.mil/ironbank/opensource/istio/proxyv2:1.19.0"