Remove asset-svc from our codebase + bitnami builds

[antgamdia]

Summary

As we are shifting towards the kubeapps-apis component, some old components are no longer useful. Specifically, the assetsvc component was scaled down to 0 replicas in the latest releases.

Background and rationale
Now it's time to remove the old assetsvc code in our codebase, so that we can start pruning some dead-code, etc.

Description
This task requires some coordination (so that the release process doesn't get stuck) with the Bitnami team, as they have to remove this component from their system as well and follow their deprecation guidelines.

Acceptance criteria

• The assetsvc component has been removed from the Kubeapps codebase: Remove assetsvc #4880
• There is no dead-code as a result of this removal (especially under the /pkg folder) Clean and tidy up the pkg/ dir #4883
  • Move "no longer common packages" to the directory they belong (eg. some db management to the kubeapps-apis plugins)
• Bitnami has been notified about our deprecation intentions and we have acknowledged their internal task.

Additional context

[antgamdia]

Our intentions to remove this component have been properly communicated internally. They will work independently to deprecate on their side the component.

I'll start removing the related code from our codebase soon.

[antgamdia]

Quick report on the pkg/* usage (details below):
The image depicts the future situation, after merging #4883

If a vertex is (or becomes) connected by a single edge, then the pkg is no longer "global" and should be placed on the call-site directory. For instance pkg/agent and pkg/handlerutil can be moved to kubeapps-apis once kubeops is removed.

• pkg/agent
  • cmd/kubeapps-apis/plugins/helm/packages
  • cmd/kubeapps-apis/plugins/pkg/clientgetter
  • cmd/kubeops
• pkg/chart
  • cmd/asset-syncer
  • cmd/kubeapps-apis/plugins/fluxv2/packages
  • cmd/kubeapps-apis/plugins/helm/packages
  • cmd/kubeapps-apis/plugins/pkg/pkgutils
  • cmd/kubeops
  • pkg/agent
  • pkg/chart
  • pkg/dbutils
  • pkg/handlerutil
  • pkg/helm
  • pkg/tarutil
• pkg/dbutils
  • cmd/asset-syncer
  • cmd/kubeapps-apis/plugins/helm/packages
• pkg/handlerutil
  • cmd/kubeapps-apis/plugins/helm/packages
  • cmd/kubeops
• pkg/helm
  • cmd/asset-syncer
  • cmd/kubeapps-apis/plugins/fluxv2/packages
  • pkg/chart
• pkg/http-client
  • cmd/asset-syncer
  • cmd/kubeapps-apis/plugins/fluxv2/packages
  • cmd/kubeapps-apis/plugins/helm/packages
  • pkg/chart/
  • pkg/kube
  • pkg/tarutil
• pkg/kube
  • cmd/apprepository-controller
  • cmd/asset-syncer
  • cmd/kubeapps-apis/core/plugins
  • cmd/kubeapps-apis/plugins/fluxv2/packages
  • cmd/kubeapps-apis/plugins/helm/packages
  • cmd/kubeapps-apis/plugins/pkg/clientgetter
  • cmd/kubeops
  • pkg/agent
  • pkg/chart
  • pkg/http-handler
• pkg/tarutil
  • cmd/asset-syncer
  • cmd/kubeapps-apis/plugins/fluxv2/packages