Rename `builds:` flag in `gitlab.yml` & 'gitlab.rb` to be `pipelines:`
Description
We are moving away from the naming scheme of "builds", and as such we should clean up gitlab.yml and gitlab.rb as well. Note the UI for this has already been changed to Pipelines.
Proposal
When configuring default project feature settings, this flag should be renamed to pipelines.
We should also support listening for the old builds flag, as that would preserve existing behavior for customers and reduce issues upon upgrade. In this case we will continue to read/write to the builds directory.
If the pipeline flag is set, it then takes priority and we will switch over to the pipelines directory for all reading/writing of logs. This provides a method to allow admins to gracefully migrate their data over.
As part of 9.0 we will announce that the builds flag is deprecated, and admins should perform this migration soon.