drm_hwcomposer: Move HwcLayer out of DrmHwcTwo class

... to reduce complexity of DrmHwcTwo.* files.

Bump-up tidy level of new files to NORMAL (fix function naming,
add NOLINT, etc.)

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
diff --git a/backend/BackendClient.cpp b/backend/BackendClient.cpp
index 49963b8..73a3b3d 100644
--- a/backend/BackendClient.cpp
+++ b/backend/BackendClient.cpp
@@ -24,7 +24,7 @@
                                            uint32_t *num_types,
                                            uint32_t * /*num_requests*/) {
   for (auto & [ layer_handle, layer ] : display->layers()) {
-    layer.set_validated_type(HWC2::Composition::Client);
+    layer.SetValidatedType(HWC2::Composition::Client);
     ++*num_types;
   }
   return HWC2::Error::HasChanges;