Protect object templates from being overridden

Problem/Motivation

Protect Pinto objects from being overridden for example by the active theme.

For example if you have a Pinto object with a template that resolves to `media`, and you have `olivero` enabled, which has a `media.html.twig`, the olivero one will take priority.

This is likely never the desired behaviour.

Proposed resolution

Protect Pinto objects and their templates by making the Pinto theme hook name unique, ie. extra prefix before default template name so simple names like `media` are transformed into something unique.

Even prefixing with a stable-random prefix should be enough, just like stream wrappers.

Ultimately the only true way to get around this is to not use theme, but rather a custom render element. Just like SDC does, and doesnt use #theme.