Fix inspect template .HostIp for Docker compatibility

[Honny1]

Docker-compatible inspect templates using {{.HostIp}} fail in Podman because Go templates resolve by struct field name (HostIP), not JSON tag (HostIp). Add a HostIp() method so both notations work.

Fixes: #29164

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Does this PR introduce a user-facing change?

Fixed `inspect --format` to support Docker-compatible `{{.HostIp}}` in `NetworkSettings.Ports` templates (https://github.com/podman-container-tools/podman/issues/29164).

[packit-as-a-service]

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