Resolves #35762

Introduces a new generic package api endpoint that allows an authorized user to list/enumerate uploaded packages under a specified organization and package-name.

This is useful for linking gitea's generic package registry with additional automation that can operate using the content uploaded here - particularly when combined with ci/cd actions - for example automatically downloading and deploying the latest compiled build of repos within your organization.

The API itself is intended to be as simple and straight forward as possible; only returning the most relevant information pertaining to the versions/files available.

NOTE: the contributing guide mentions that all new APIs should be documented using swagger docs, but I noticed that none of the package APIs include any swagger-docs, so I wasn't sure what the preference on implementation there would be.

Example usage:

$ curl http://localhost:3000/api/packages/TestOrg/generic/examplePackage/list
[{"version":"v0.1.0","downloads":0,"files":[{"name":"example.tar.gz","created":1761612511}]}]