Allow packages multipart uploads

What does this MR do?

Multipart uploads have some restrictions implemented in the GitLab multipart middleware (see https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/gitlab/middleware/multipart.rb#L87-91).

Recently, we launched the support for NuGet packages. Those packages are uploaded by nuget using a multipart upload. As the package storage path is not in the allowed_paths structure, the upload is rejected.

Note that this happens when not using the workhorse acceleration direct upload. This is why, this issue is not happening on GitLab.com. In short, we have this possible configurations for uploads:

Object Storage	Direct Upload Enabled	Direct Upload Disabled
Enabled	works	fails
Disabled	fails	fails

This MR adds package storage path in the allowed_paths to fix the above fails cases and the relevant tests.

See #208744 (closed)

Design choices

• Since upload paths are quite sensitve, the allowed_paths is updated only and only if where not using workhorse direct uploads.
• Add relevant tests for Gitlab::Middleware::Multipart and in the nuget_packages_shared_examples.

Screenshots

Failing upload

$ nuget push Bananas.1.0.0.nupkg -source local
WARNING: No API Key was provided and no API Key could be found for 'http://gitlab.local:8000/api/v4/projects/1/packages/nuget'. To save an API Key for a source use the 'setApiKey' command.
Pushing Bananas.1.0.0.nupkg to 'http://gitlab.local:8000/api/v4/projects/1/packages/nuget'...
  PUT http://gitlab.local:8000/api/v4/projects/1/packages/nuget/
  InternalServerError http://gitlab.local:8000/api/v4/projects/1/packages/nuget/ 3117ms
  PUT http://gitlab.local:8000/api/v4/projects/1/packages/nuget/
  InternalServerError http://gitlab.local:8000/api/v4/projects/1/packages/nuget/ 2470ms
  PUT http://gitlab.local:8000/api/v4/projects/1/packages/nuget/
  InternalServerError http://gitlab.local:8000/api/v4/projects/1/packages/nuget/ 924ms
Response status code does not indicate success: 500 (Internal Server Error).

Upload fixed

$ nuget push Bananas.1.0.0.nupkg -source local
WARNING: No API Key was provided and no API Key could be found for 'http://gitlab.local:8000/api/v4/projects/1/packages/nuget'. To save an API Key for a source use the 'setApiKey' command.
Pushing Bananas.1.0.0.nupkg to 'http://gitlab.local:8000/api/v4/projects/1/packages/nuget'...
  PUT http://gitlab.local:8000/api/v4/projects/1/packages/nuget/
  Created http://gitlab.local:8000/api/v4/projects/1/packages/nuget/ 3456ms
Your package was pushed.

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

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• 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