Implement RFC-004 across all controllers and CLI

[aryan9600]

Now that RFC-004 has been merged, we can start implementing it.

TODOs:

Controllers

• Create a new flag to block use of HTTP endpoints for provider notification-controller#386
• [RFC-004] Add new flag --insecure-allow-http image-automation-controller#457
• [RFC-004] Add new flag --insecure-allow-http source-controller#956
• [RFC-004] Add new flag --insecure-allow-http image-reflector-controller#324
• [RFC-004] Add .spec.insecure to ImageRepository image-reflector-controller#325
• [RFC-004] Add .spec.insecure to HelmRepository source-controller#957

CLI:

• Add --insecure flag to flux create source helm
• Add --insecure flag to flux create image repository