Use correct permission and path for enabling Alert Management

What does this MR do?

We want two things to happen in this MR:

• Allow empty-state button on 'Operations > Alerts' page to appear for maintainer+ (if the user can configure the generic alerts endpoint)
• Point the empty-state button to the page at which they can configure the generic alerts endpoint

There's also a light splash of fixing some stuff in the specs for the file. 😄

No changelog is included as this is still behind a feature flag.

Related issue: #216053 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry due to feature flag
• [-] 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