Enable/disable owner and repo projects independently (#28805)

Part of #23318 

Add menu in repo settings to allow for repo admin to decide not just if
projects are enabled or disabled per repo, but also which kind of
projects (repo-level/owner-level) are enabled. If repo projects
disabled, don't show the projects tab.


![grafik](b9b43fb4-824b-47f9-b8e2-12004313647c)

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Co-authored-by: delvh <dev.lh@web.de>

services/forms/repo_form.go

@@ -142,6 +142,7 @@ type RepoSettingForm struct {
 	ExternalTrackerRegexpPattern          string
 	EnableCloseIssuesViaCommitInAnyBranch bool
 	EnableProjects                        bool
+	ProjectsMode                          string
 	EnableReleases                        bool
 	EnablePackages                        bool
 	EnablePulls                           bool