Add a Summary tab for incident issues

What does this MR do?

Creates a tabs widget for incident issues. Adds a 'Summary' tab that displays the description.

Also introduces a minimal graphql apollo client for the main "issue_show" vuejs app.

The tabs widget only shows when the issue is of type Incident.

Note: This has not been implemented for the haml version of the page, I'm not sure how important this is.

Issue: #230845 (closed)

To Test

• Navigate to Operations -> Incidents
• Create a new Incident
• Observe the new Summary tab

Screenshots

issuable type	before	after
incident
issue (no change)
epic (no change)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [n/a] Documentation (if required) Will make one docs change later as part of &3993 (closed), to reduce churn.
• 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