Add TLS certificates for internal release registry in agent installer

[zaneb]

Implement TLS certificate infrastructure to enable secure communication with the built-in registry used by the agent installer. This addresses the need for proper certificate management across the agent ISO boot, bootstrap, and cluster startup phases.

Create three new certificate assets:

• InternalReleaseRegistrySignerCertKey: CA certificate that signs registry server certificates and tracks when loaded from disk
• InternalReleaseRegistryCertKey: Server certificate valid for both localhost and api-int. for use during bootstrap
• InternalReleaseRegistryLocalhostCertKey: Server certificate valid only for localhost for use in the unconfigured ignition (ISO phase)

The implementation ensures certificates are distributed appropriately:

• Unconfigured ignition includes CA cert+key in /opt/agent/tls/ for assisted-service to load, CA cert in system trust store, and localhost-only server cert in /opt/registry/tls/
• Bootstrap and master ignitions conditionally include the api-int server certificate when the CA was loaded from disk
• AdditionalTrustBundle ConfigMap automatically includes the CA when loaded from disk to ensure cluster-wide trust
• Bootkube restarts registry.service if running to pick up new certs

All certificate inclusions in bootstrap/master ignitions and trust bundles are conditional on the CA being loaded from disk, ensuring this only affects agent-based installations.

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