Decouple package and repository permissions

What does this MR do?

Relates to #332028 (comment 590728831)

This MR decouples the package registry permissions from the repository permissions.

Notes from the issue:

• Deploy tokens get access to packages through a special condition in the project policy.
  • This works as expected
• Now we have a negative rule that basically says if one of the below is true, all packages permissions are removed:
  • The packages feature is disabled
  • The repository feature is disabled
• The ~bug lies when checking the repository feature. This check is mainly done by verifying if the user has access to the project feature.
• Let's break down how this "has the current user access to this project feature" function:
  1. if the feature is currently DISABLED, well, we return false
  2. if the feature is currently PRIVATE, we check that the current user has the proper minimum access level for the feature
  3. all other cases (including feature is ENABLED), we return true
• The problem is that when (2.) is evaluated against a DeployToken object, the backend thinks that it has no access level at all.
  • This case will reject the user from getting the package permissions.

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• 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