migrate vim and vim-core to portage-stable BUG=b/526654058 TEST=presubmit RELEASE_NOTE=None cos-patch: bug Change-Id: I5b51223a49b6f57c47eee00ec8dd4ce14359a76f Reviewed-on: https://cos-review.googlesource.com/c/third_party/overlays/chromiumos-overlay/+/165609 Reviewed-by: Dom Huh <domhuh@google.com> Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com> Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>