Add support for ArtifactHub (the replacement for Helm Hub)

[troytop]

Not sure if this is just a hiccup or if it's an earlier EOL than we expected, but https://hub.helm.sh/ is not returning searches, thus hanging the monocular view in Stratos.

A Monocular compatible search API endpoint has been added to Artifact Hub via artifacthub/hub#598

[richard-cox]

• In 4.2 Helm Hub is now disabled by default (to be removed entirely in future release) (Remove Helm Hub support #524)
• In a future release we'll replace the hub functionality with artifact hub
• The stratos upstream repo can now be found in Artifact hub - https://artifacthub.io/packages/helm/stratos/console (Add Stratos Helm Repo to Artifact Hub cloudfoundry/stratos#4645)

UPDATE!

• In 4.2 support for Helm hub has been removed (Remove Helm Hub support #524)
• In 4.2 support for Artifact Hub has been added (Add support for Artifact Hub cloudfoundry/stratos#4646)
• The stratos upstream repo can now be found in Artifact hub - https://artifacthub.io/packages/helm/stratos/console (Add Stratos Helm Repo to Artifact Hub cloudfoundry/stratos#4645)