Namespace Remaining miscellaneous Ci code

Related to issue: #207480 (closed)

• CommitWithPipeline could remain outside CI but CommitWithPipeline#pipelines should not know about Ci::Pipeline details. !51146 (merged)
• CommitStatusEnums !51146 (merged)
• ExternalPullRequest !59895 (closed)
• TriggersHelper !51146 (merged)
• Gitlab::Artifacts::MigrationHelper !59920 (merged)
• Gitlab::Badge::* !51219 (merged)
• [-] Project::ArtifactsController

Move related specs by consequence.

Can't be easily moved - needs more thoughts. See this epic: &9991

• [-] CommitStatus + GenericCommitStatus because we would need to migrate the type column in ci_builds. We could move it under Ci:: and leave CommitStatus as inheritance only class from Ci::CommitStatus that would allow us to read old records until the next major release.