Return description field in nuget package catalog entry

What does this MR do and why?

Problem

When consuming a NuGet feed from GitLab in Visual Studio, the description of a package is not shown in the details view. It is only shown in the list view.

Solution

Return the description field in the package's catalog entry.

Currently, in the GitLab NuGet repository, we return the same value for both description & summary in the package's catalog entry. The value is the metadata description attribute we extract from the package's nuspec file on publishing.

Screenshots or screen recordings

How to set up and validate locally

Follow the same steps mentioned here. You should find the description of the package appears in the details view in visual studio.

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.

Related to #420156 (closed)