Add 'Accepting Builds' panel for zuul-status
Add 'Accepting Builds' panel for zuul-status

We have a new metric to track if executors are accepting builds or
not.

Change-Id: Icd8671c026e2ed93b0acff536df795b3fa030539
Signed-off-by: Paul Belanger <e7139c8e6c4ea75cc1c287ce081b2dc0f3ab39ec@redhat.com>

openstack-infra/project-config,openstack-infra/project-config