Option to set .gitlab-ci.yml's Parsed YAML Size Limit

Update

The problem in this issue has been addressed in !68593 (diffs)+ for self managed new issue created to consider increasing the default CI YAML limits. #370116

Problem to solve

Gitlab 12+'s

The parsed YAML is too big

Intended users

Administrators who have enough resources that the size of the parsed YAML doesn't matter.

Further details

We recently upgraded to 12.0.3 (gitlab-ce@08a51a9db938bb05f9a4c999075d010079e16bad) and to our surprise our big project's .gitlab-ci.yml stoped parsing. In lieu of support to specify a cartesian product (gitlab-ce#19199), we wrote a script to take all our unit tests and create jobs to run for each platform we are supporting. This generates a very large CI file, and up until version 12 GitLab has happily chugged along without a hitch.

Proposal

Create a "Maximum .gitlab-ci.yml Parsed Size" option in the "CI/CD Admin Area", just like the "Maximum Artifacts Size" setting.

Permissions and Security

The administrator with access to the "CI/CD Admin Area".

Documentation

Not sure what to put here, sorry.

Testing

Once again not sure what to say here. IMO it would improve the product by allowing local administrators to control GitLab in their environment.

What does success look like, and how can we measure that?

Just as success was measured for the "Maximum Artifacts Size". Does GitLab provide flexibility to its Administrative users?