gnome-base/gnome-shell: fix crash, EAPI-7, python3.7

gnome-base/gnome-shell: fix crash, EAPI-7, python3.7

Refreshed patchset that contains (compared to previous):
* a new commit from gnome-3-30 branch, which fixes some issues
  related to workspace finger gesture on wayland;
* backport of a public API safeguard which downgrades a mysterious
  crasher (that may happen on suspend resume, or just trying to unlock)
  to an API misuse warning;
* includes the bluetooth optionality patch in the patchset.

Port to EAPI-7.
Add python:3.7 support for the odd installed tools; not fully tested,
as they are complicated to use and really only shell developers use
them, but we install them for now still.

Package-Manager: Portage-2.3.52, Repoman-2.3.12
Signed-off-by: Mart Raudsepp <leio@gentoo.org>