Restrict usage of project creator method

Like in #350603 (closed), we have some usages of project.creator that mean something like "just get the creator, is probably the owner". Due to the semantic difference between them, it's a good thing to restrict the creator method to cases when the creator of the project is strictly needed.

I see 309 occurrences of .creator according to a grep. Upon a quick skim most seem to be project.creator and some of them will not need changing.

See &7405 (comment 818917873) for a small thread on this topic.

The vast majority of instances of creator are in specs/factories/fixtures excepting the below 👇

Instances of .creator in code (not specs)

Code location	Action	MR	Team
app/views/shared/projects/_project.html.haml#L19 lines 19, 26, 27	This seems to refer to the project creator, so no action	n/a	Organization
app/services/projects/create_service.rb#L66	Setting the creator on create. No action.	n/a	Organization
app/views/admin/projects/show.html.haml#L58	Displaying the name of the creator. No action needed.	n/a	Organization
spec/support/import_export/common_util.rb#L63 lines 63, 69	Creator used for TreeRestorer service.	-	Import
lib/gitlab/github_import/importer/pull_request_importer.rb#L95	Creating a source branch.	-	Import
app/workers/repository_import_worker.rb#L27	Creating a repository via import.	-	Import
lib/gitlab/import_export/importer.rb#L15	Current user set as import project creator. Probably no action?	-	Import
app/services/projects/protect_default_branch_service.rb#L38	Ensuring a protected branch can be made.	-	Source code
ee/app/workers/repository_update_mirror_worker.rb#L24	Updating a repo via mirror.	-	Source code
app/workers/repository_update_remote_mirror_worker.rb#L45	Updating a remote repo via mirror.	-	Source code

Availability and Testing

• Run package-and-qa job within the MRs for the code changes listed above. If the change is small enough / has low risk, this job may be skipped. Please review with a domain expert and ~"group::workspace" SET before deciding to skip package-and-qa