Add tracking for additional NuGet events

Issue: #198660 (closed)

What does this MR do?

This MR aims to add tracking for SnowPlow events for when:

• GitLab has been set as a remote NuGet repository
• A NuGet package has been downloaded
• A NuGet package has been searched for

It also will add tests to ensure this functionality is working properly.

What does this MR not do

• It does not add tracking to the Usage Ping, which is required for tracking self-managed instances.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team