Allow dynamic files for Conan package uploads

What does this MR do?

When publishing Conan packages to the GitLab package registry, the Conan client will make a request to fetch the upload urls for each file to be uploaded. Currently, we return a static list of files based on a list of pre-set files. https://gitlab.com/gitlab-org/gitlab/blob/master/lib/gitlab/regex.rb#L6-7

This MR updates to follow the behavior that is actually expected by Conan. The Conan client provides a list of files that need to be uploaded in the request body along with their respective filesizes. Here, we update the API code to return the list of upload urls based on the list of files requested instead of using the static list. This fixes a problem where users were unable to upload optional, but common package files such as conan_sources.tgz and conan_export.tgz.

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

Related #210550 (closed)