Refactor cmd global variables into structs

cmd/flux/bootstrap.go

cmd/flux/bootstrap_github.go

cmd/flux/bootstrap_gitlab.go

cmd/flux/check.go

cmd/flux/create.go

cmd/flux/create_alert.go

cmd/flux/create_alertprovider.go

cmd/flux/create_helmrelease.go

cmd/flux/create_image_policy.go

cmd/flux/create_image_repository.go

cmd/flux/create_image_updateauto.go

cmd/flux/create_kustomization.go

cmd/flux/create_receiver.go

cmd/flux/create_secret_git.go

cmd/flux/create_secret_helm.go

cmd/flux/create_source_bucket.go

cmd/flux/create_source_git.go

cmd/flux/create_source_helm.go

cmd/flux/create_tenant.go

cmd/flux/delete.go