Check correct permissions before showing Release Evidence link

What does this MR do and why?

Change EvidenceType to check if user is authorized to read_release_evidence. This rule is already used when downloading Release Evidence (see controller).

The read_release_evidence rule checks download_code and a few other rules internally (see policy).

Related to #208397 (closed)

Screenshots or screen recordings

When user can read_release_evidence

When user cannot read_release_evidence

How to set up and validate locally

1. Create a Release.
2. Wait for Release Evidence to be created.
   • The Release should show a link to the Evidence (see screenshots above).
3. Turn off Issues in the project's settings.
   • read_release_evidence requires read_issue, so it will return false when Issues are turned off.
4. The Release should not show a link to the Evidence anymore.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.