findmissing/git_interface: Implement get_integrated_tag

get_integrated_tag() returns, for a given SHA, the first tag
that contains it.

BUG=None
TEST=Run on GCE

Change-Id: Ieed30d56b12a4767575abd2fdcafa4e09b42cfbc
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2200141
Reviewed-by: Curtis Malainey <cujomalainey@chromium.org>
Commit-Queue: Guenter Roeck <groeck@chromium.org>
Tested-by: Guenter Roeck <groeck@chromium.org>
1 file changed