Release the NPM metadata abbreviated support

🍌 Context

In !73639 (merged), we added support for the NPM package metadata. That changed impacted the upload and the metadata endpoints.

Due to the NPM Package Registry popularity on gitlab.com, the changed was deployed using a feature flag.

Here is the rollout issue: #344827 (closed).

The feature flag has been globally enabled for more than a day on gitlab.com without any hiccup.

Because the NPM package metadata can be wildly different (users can throw in any number of custom fields), we'd like to release this change using the "feature flag enabled by default approach". This way, if a self-managed user has a scenario with conditions that cause a problem, the feature flag can act as a safety toggle.

🔭 What does this MR do and why?

• Enable packages_npm_abbreviated_metadata by default.

🎥 Screenshots or screen recordings

• !73639 (merged)

✅ How to set up and validate locally

• !73639 (merged)

🚓 MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.