Add weekly error budget for product analytics and analytics instrumentation

Description

What

Adds weekly error budget reporting for groupproduct analytics and groupanalytics instrumentation following this guide.

Why?

Regular check-ins on our groups error budgets allow us to catch problems sooner and be proactive about preventing errors.

This came up as an issue in:

• groupanalytics instrumentation has discussed this problem in Add alert on high amount of Analytics Instrumen... (gitlab-org/gitlab#467919).
• groupproduct analytics discussed in this slack thread (internal link) that an unhealthy error budget went unnoticed.