[kbn/server-route-repository] Clean up partial implementations

[miltonhultgren]

Because the route repository package has evolved overtime and adoption has been continuous during that time, we can find some plugins that use some parts of functionality coming from the package and some parts that are "copies" of code that now has been ported into the package.

To ensure consistent usage of the package, we should refactor any plugin that uses the package but doesn't pull all the functionality from the package itself.

This may require extensions to the package in case there are additional features in the copies that have not been included in the package.

Affected plugins

• apm (duplicate of createRepositoryClient, duplicate of registerRoutes) [@elastic/obs-ux-infra_services-team]
• dataset_quality (duplicate of createRepositoryClient, duplicate of registerRoutes) [@elastic/obs-ux-logs-team]
• investigate_app (duplicate of createRepositoryClient) [@elastic/obs-ux-management-team]
• observability (duplicate of registerRoutes, doesn't create a client) [@elastic/obs-ux-management-team]
• observability_onboarding (duplicate of createRepositoryClient, duplicate of registerRoutes) [@elastic/obs-ux-logs-team, @elastic/obs-ux-onboarding-team]
• slo (duplicate of registerRoutes, doesn't create a client) [@elastic/obs-ux-management-team]
• ux (duplicate of createRepositoryClient to talk to an APM API) [@elastic/obs-ux-infra_services-team]

[elasticmachine]

Pinging @elastic/obs-knowledge-team (Team:obs-knowledge)

[miltonhultgren]

FYI @elastic/obs-ux-infra_services-team @elastic/obs-ux-logs-team @elastic/obs-ux-management-team @elastic/obs-ux-onboarding-team