drm_hwcomposer: Tidy-up DrmConnector class

Implement DrmConnector instantiation through CreateInstance() static method,
which helps to reduce complexity of DrmDevice::Init() function.

Move Connector-to-CRTC binding information to the DrmDevice class.

Move drm/DrmConnector.h to Normal clang-tidy checks list by fixing
clang-tidy findings.

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
diff --git a/hwc2_device/HwcDisplay.h b/hwc2_device/HwcDisplay.h
index 76456b7..3e8a548 100644
--- a/hwc2_device/HwcDisplay.h
+++ b/hwc2_device/HwcDisplay.h
@@ -209,8 +209,7 @@
    * https://source.android.com/devices/graphics/hotplug#handling-common-scenarios
    */
   bool IsInHeadlessMode() {
-    return handle_ == kPrimaryDisplay &&
-           connector_->state() != DRM_MODE_CONNECTED;
+    return handle_ == kPrimaryDisplay && !connector_->IsConnected();
   }
 
  private: