Something are introduced in this patch:
* As devstack-gate/devstack-vm-gate-wrap.sh is not really zuul v3
native, we move all configs in to `devstack/lib/heat` and .zuul.yaml.
* Remove extra configs process in devstack. Like setup tempest(which
is well covered by tempest itself.) or overlapping heat test configs setup.
Use tempest config for all heat_integration tests. Also remove
heat_integrationtests/common/configs since they're no longer required.
* copy post.yaml for grenade jobs. As we migrate to zuul v3 for
functional tests but not grenade (not yet), the post.yaml should exists
under grenade dir. since it's only required by grenade jobs.
* Use post.yaml in functional tests for cleanup test environments.
Story: #2007056
Task: #37908
Depends-On: https://review.opendev.org/701105
Change-Id: I4f531161a7222e2c2a21f8d483f9c2a1d91dc38d