Fix validators interface. Add refAddonStage testutils. Fix 001_default_channel.

[sugarraysam]

This PR adds a few changes and can be a bit confusing because many files are touched, but they all work together.

Changes

• Add testutils.GetReferenceAddonStage to help writing validators, especially getting a quick and easy SucceedingCandidate, that includes a full MetaBundle object
• Fix the 001_default_channel validator
• Modifies the validator interface so validators can return a failureMsg that will give users instructions on how to fix the failure
• Refactored the meta_loader_test.go to use the testutils.GetReferenceAddonStage helper

Issue found with &registry.Annotations{}

It seems our extraction code extracts bundles using the deprecated packageManifest format:

# Inspect the local cache
$ tree /tmp/mtcli-07b10894-0673-4d95-b6ef-0cbd9701c9c3
/tmp/mtcli-07b10894-0673-4d95-b6ef-0cbd9701c9c3
└── quay.io
    └── osd-addons
        └── reference-addon-index@sha256:0c8b02008f2c2faeb681ae8cd454821266a794435aea4b3f7ae28c74bc2e280d
            └── reference-addon
                ├── 0.1.0
                │   └── reference-addon.csv.yaml
                ├── 0.1.1
                │   └── reference-addon.csv.yaml
                ├── 0.1.2
                │   └── reference-addon.csv.yaml
                ├── 0.1.3
                │   └── reference-addon.csv.yaml
                ├── 0.1.4
                │   └── reference-addon.csv.yaml
                ├── 0.1.5
                │   └── reference-addon.csv.yaml
                └── package.yaml

The issue with this format is that we do not get access to the annotations.yaml file. Now I might be wrong, but I believe we need to validate some of these annotations as OLM depends on them to run the workloads properly. For example, look at the commented out pkg/validators/validator_001_default_channel.go::matchesDefaultChannelAnnotations::#line 61 which validates default channel annotations.

cc @yashvardhan-kukreja @ashishmax31

Bundles format expected output (from mtbundles)

├── 0.1.0
│   ├── manifests
│   │   └── reference-addon.csv.yaml
│   └── metadata
│       └── annotations.yaml
├── 0.1.1
│   ├── manifests
│   │   └── reference-addon.csv.yaml
│   └── metadata
│       └── annotations.yaml
├── 0.1.2
│   ├── manifests
│   │   └── reference-addon.csv.yaml
│   └── metadata
│       └── annotations.yaml
├── 0.1.3
│   ├── manifests
│   │   └── reference-addon.csv.yaml
│   └── metadata
│       └── annotations.yaml
├── 0.1.4
│   ├── manifests
│   │   └── reference-addon.csv.yaml
│   └── metadata
│       └── annotations.yaml
├── 0.1.5
│   ├── manifests
│   │   └── reference-addon.csv.yaml
│   └── metadata
│       └── annotations.yaml

[yashvardhan-kukreja]

Fab work @sugarraysam !
Just some minor suggestions and doubts. Rest we're good to go :)

[ashishmax31]

@sugarraysam Interesting, let me go through the code today and find out why its exporting bundles in the package manifests format.

[yashvardhan-kukreja]

lgtm! Great work @sugarraysam , thanks 🚀