caddyfile: preserve implicit TLS issuer semantics - #7743

Fixes #7738

• preserve implicit issuer semantics when consolidating Caddyfile-generated automation policies
• avoid merging implicit public and internal subject sets into one no-issuer policy
• treat implicit internal-only policies and explicit default internal issuer policies as equivalent for consolidation
• add regression coverage for repeated localhost subjects on different ports

Assistance Disclosure

No AI was used.