findmissing: git_interface: Provide get_cherrypick_status as generic function

Extracted from missing.py for generic use, then replace calls to
missing.get_status_from_cherrypicking_sha() with
git_interface.get_cherrypick_status(), and drop
missing.get_status_from_cherrypicking_sha().

BUG=None
TEST=Run on GCE

Change-Id: Iced2c79d225196c60e849764e3018ccb211fac37
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2200142
Commit-Queue: Guenter Roeck <groeck@chromium.org>
Tested-by: Guenter Roeck <groeck@chromium.org>
Reviewed-by: Curtis Malainey <cujomalainey@chromium.org>
2 files changed