Use more verbose alert messages

What does this MR do?

Improves error messages for groupobservability as part of gitlab-org/opstrace/opstrace#2474 (closed). Specifically, this discussion: gitlab-org/opstrace/opstrace#2474 (comment 1623504320)

NOTE: I know my initial changes are wrong. However, it's tough to revise strings in an issue. More easily done here.

Message	Location
Failed to enable GitLab Observability.	app/assets/javascripts/observability/components/provisioned_observability_container.vue
Failed to load page.	app/assets/javascripts/observability/components/provisioned_observability_container.vue
Failed to load trace details.	ee/app/assets/javascripts/tracing/components/tracing_details.vue
Something went wrong while fetching the operations	ee/app/assets/javascripts/tracing/components/operation_search_token.vue
Something went wrong while fetching the services	ee/app/assets/javascripts/tracing/components/service_search_token.vue

Related issues

Related to Review text/messages with technical writer (gitlab-org/opstrace/opstrace#2474 - closed) (specifically the threads about error messaging)

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