Script Modules API: Add a translations API

[luisherranz]

Now that WordPress is going to support native ES modules through the new Modules API, we should start discussing possible translation APIs to support internationalization/localization, similar to what wp_set_script_translations provides for the Scripts API.

Some of the initial considerations are:

• It should support the dynamic loading of translations when used in conjunction with dynamic imports (import()) to avoid downloading all the translations on page load.
• Ideally, it should download the translations required in the initial page load in parallel to avoid waterfalls on page load.
• Ideally, it should rely only on available PHP and JavaScript APIs, and not require any specific tooling.
• Ideally, the APIs should be as transparent as possible to the developers.

Please share your opinions and ideas. Let's use this ticket for discussion.

[jonsurrell]

This is related to and may depend on #60647 which would make wp-i18n functionality available to script modules.

[swissspidy]

#63401 was marked as a duplicate.