drm_hwcomposer: Rework CreateLayer/DestroyLayer

- Make HwcDisplay CreateLayer/DestroyLayer frontend-agnostic.
- Provide LayerId as an input for CreateLayer. It is necessary to add
  the HWC3 LayerLifecycleBatchCommand feature, where layer ID is
  generated by the client.

Change-Id: I317dcf22461fe4390ced9f0c0c780cffaa3b8f5d
Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
diff --git a/hwc3/DrmHwcThree.h b/hwc3/DrmHwcThree.h
index 44168aa..10470ea 100644
--- a/hwc3/DrmHwcThree.h
+++ b/hwc3/DrmHwcThree.h
@@ -26,6 +26,8 @@
 class Hwc3Display : public ::android::FrontendDisplayBase {
  public:
   bool must_validate = false;
+
+  int64_t next_layer_id = 1;
 };
 
 class DrmHwcThree : public ::android::DrmHwc {