In case when `needs:` is missing, but when requested by service,
we would not save the pipeline with config_error.

This makes it explicit that we want to persist the error
as `config_error` failure reason.

Enables frozen string for the following:

* lib/gitlab/ci/*.rb
* lib/gitlab/ci/build/**/*.rb
* lib/gitlab/ci/config/**/*.rb
* lib/gitlab/ci/pipeline/**/*.rb
* lib/gitlab/ci/reports/**/*.rb

Partially addresses #47424.