Clean up code around optional permissions

[Kevin-CB]

Some cleanup around optional permissions:

• Deprecate helper methods and have them check real state, not system property
• Remove undocumented artifactList attribute permission since only Run#ARTIFACTS is supported
• On the artifacts-index view, the permission check was done outside of l:layout, which is what defines the h variable. So, this permission check was not effective (note that it's not a vulnerability as the Run#ARTIFACTS is not there to restrict the listing of artifacts but the access/download to them, see Clarify artifacts permission description #9276) .

Testing done

I only tested the artifacts-index view as other changes are minimal.

It can be reached by navigating to the endpoint /job/myJob/1/artifacts-index and require the Run#ARTIFACTS permission to be enabled (Run.ARTIFACTS.enabled = true on the script console)

Before:

After:

Proposed changelog entries

N/A

Proposed upgrade guidelines

N/A

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Desired reviewers

@daniel-beck

Before the changes are marked as ready-for-merge:

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