Run package-and-qa on master more frequently

Traceability of the validation for gitlab-qa runs against gitlab-org/gitlab@master -> staging -> production is unclear. In an effort to improve this traceability to reduce issue occurrences like https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/7907

Requirements

• Trigger gitlab-qa image to be built more frequently
• Create a new scheduled pipeline every 2 hours to trigger tests against master - Engineering Productivity
• Validate that executed test sets contain the necessary tests for each stage/group - Counterpart TAEs
• Ensure handbook documents what test sets are run in which environment on given scheduled frequencies.

Future iterative improvements

• Collaborate with Delivery team to ensure deployments to staging contain only green master builds

Proposal

• Modify gitlab-qa/nightly frequency to be nightly
• Utilize an existing scheduled pipeline to trigger the package-and-qa more frequently against master - gitlab-org/gitlab!17237 (merged)
• Send a Slack notification when a gitlab-qa pipeline that run for master schedules succeed or fail. - tracked in gitlab-org/gitlab#32776 (closed), gitlab-org/gitlab!17796 (merged)
• Adjust test run in package-and-qa based on necessary test sets for execution against master - Test Automation Engineers

Discussed during Quality Engineering Staff meeting on 2019-09-18 - https://docs.google.com/document/d/1mvKwDBCoYqIs9zB_PTUUhUoBKs_bOxtz3x15mNLkUu0/edit?ts=5d824705#bookmark=id.1kt130ch6hzn