[Telemetry] Restore reliable contentlets_count reporting for product and CX metrics

Related

• Parent Epic: #34837
• Root cause: #34926

Possibly a duplicate of 34926 but wanted it to keep the user story front and centre.

Subtasks

• #35010 — refactor(telemetry): Use {feature}_{name} composite key as internal metric identifier (reverts the name change that broke contentlets_count, adds getQualifiedName() for internal uniqueness)

User Story

As a Product/CX team member,
I want contentlets_count to be consistently and accurately populated in telemetry for all cloud environments,
So that I can report on content growth, stickiness, and customer health — including team bonus metrics tied to content growth.

Business Context

Blocking:

1. Bonus metric — team is measured on growing content managed by customers over time; contentlets_count is required.
2. Customer health reporting — CX and Product use content volume + % actively managed content to flag at-risk vs healthy customers.
3. Reporting fragility — cloud environments silently drop off telemetry (flag disabled, API call fails), degrading all trend data.

Acceptance Criteria

• contentlets_count is populated consistently for all cloud environments
• Environments do not silently stop reporting telemetry
• Trend data is gap-free across standard collection windows
• CX and Product can run standard reports without manual corrections