Improve CI editor schema specs to support global keywords on the same file

Currently the tests inside spec/frontend/editor/schema/ci/ci_schema_spec.js that target global keywords, like workflow:, need to have separate files for each test.

An example of this can be seen in this MR: !137815 (comment 1688720005)

The newly introduced workflow:auto_cancel:on_job_failure setting supports multiple valid options, and since workflow is a global keyword I had to split the test files, one for each valid option.

Proposed solution

Use a top-level YAML entry as "test name/description" and generate a .gitlab-ci.yml contet per each one of those top level entries.

Related to the example above, the test YAML file would look like this:

# Inside spec/frontend/editor/schema/ci/yaml_tests/positive_tests/auto_cancel.yml

auto cancel pipeline on job failure all:
  workflow:
    auto_cancel:
      on_job_failure: all

auto cancel pipeline on job failure none:
  workflow:
    auto_cancel:
      on_job_failure: none