Label incidents triggered by failed tests with test-level:*. For test-level:e2e, announce in qa-master channel

See gitlab-org/quality/engineering-productivity/master-broken-incidents#6550 (comment 1919854497)

Updated proposal:

1. Label incidents with test-level:* labels based on the jobs names:

• job name starts with rspec(-ee)? unit -> test-level:unit
• job name starts with rspec(-ee)? integration -> test-level:integration
• job name starts with rspec(-ee)? system -> test-level:system
• job name starts with rspec(-ee)? (background_)?migration -> test-level:migration
• job name includes e2e -> test-level:e2e

2. For test-level:e2e, announce of qa-master channel