Refactor plugin dependencies and automatically handle them instead of using weights

[davidferlay]

Observed

• Plugins loading is currently handled manually and by weight order
• That can lead to concurency / race condition for resolving dependencies
• add plugin weight to fix keyring service dependency skilld-labs/plasmactl-publish#4 (comment)

Expected

• Introduce a more robust dependency system which does not rely on weighted plugins
  

  launchr/internal/launchr/types.go

  Line 50 in a1e4399

  // Weight defines the order of plugins calling. @todo rework to a real dependency resolving.

[lexbritvin]

Partially fixed in #127, but doesn't check circular dependencies.