Alert Management detail page graphql initial setup

What does this MR do?

Issue: #213911 (closed)

Adds graphql query for the Alert Management detail page and integrates this query with the detail Vuejs component via Apollo.

In scope:

• Sets up a query and fetches data from the graphql backend correctly
• Populates the data into the component instance property
• Shows an empty page when data is loading

Coming later: (see #213911 (comment 332880342))

• Displaying the fetched data
• Loading states
• Error states

Note: Changes are disabled in prod behind the alert_management_minimal feature flag.

Screenshots

No visual change

Does this MR meet the acceptance criteria?

Conformity

• [n/a] Changelog entry
• [n/a] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [n/a] Database guides
• [n/a] 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
• [n/a] 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:

• [n/a] Label as security and @ mention @gitlab-com/gl-security/appsec
• [n/a] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [n/a] Security reports checked/validated by a reviewer from the AppSec team