[RCA] Using repository client for accessing investigation APIs on the alert details page

[maryam-saeidi]

Summary

The server route repository package also offers a client we can use to access investigation APIs. It is type-safe, and it gives us some out-of-the-box features, such as setting the version. Here is the related documentation:

https://github.com/elastic/kibana/blob/main/packages/kbn-server-route-repository/README.md

Example of usage: https://github.com/elastic/kibana/blob/main/x-pack/plugins/observability_solution/observability/public/pages/alert_details/hooks/use_create_investigation.tsx#L35

Acceptance criteria

• Use the repository client for accessing investigation APIs on the alert details page

[elasticmachine]

Pinging @elastic/obs-ux-management-team (Team:obs-ux-management)