new UX design for Repositories

[dlaloue-vmware]

This issue is a follow up to issue #5121 which addressed improvements for the basic support of repositories for all types.

The new UX should help improve further the creation/edit of repositories. It is proposed to switch to a full page UI instead of dialog, and switch to a plugin-aware wizard instead of a dynamic one-pager.
The UI should allow for configuration to grow (e.g. adding labels/annotations to metadata), and especially allowing each plugin to provide a more native configuration for additional options (e.g. tag or ref selection in Carvel plugin).

The following are tasks that carry over from #5121 :

• Propose a better overall UX
  • Related: No obvious way to create global app repository #2995
  • @castelblanque: having a single table for all repositories, differentiating the global ones with some distinctive icon (e.g. world icon).
  • @antgamdia: Use the existing Secret-related operations to list (if necessary) the secret names (eg: getDockerConfigSecretNames`)
• Analyze and implement the remaining Helm plugin's custom detail props (like proxy, pod labels, etc)
  • Tracked at: Repos API/Helm - Analyze and migrate the former SyncJobTemplate options to the API #5128
  • Related: Kubeapps Helm AppRepository should support configurable sync interval #3661
• Add kapp plugin add "fetch" details in the UI
  • Tracked at: Add kapp plugin's customDetails in the repos UI #5107
• Analyze and implement Flux plugin's custom detail props

[gfichtenholt]

May I also suggest that current ADD PACKAGE REPOSITORY dialog be changed into a wizard? There is way too much information for a single dialog there. I think the wizard would also naturally help with transition to display plugin-specific config options. I.e. in one wizard screen you select a plugin, the next screen uses that state to render plugin-specific options, etc