Fix google-explicit-constructor warnings in frameworks/base

* Add explicit keyword to conversion constructors.
* Add NOLINT to implicit conversion constructors.

Bug: 28341362
Test: build with clang-tidy
Change-Id: Ie4d37072ab57d1662d18db4de1c8577247f43337
diff --git a/libs/hwui/Caches.h b/libs/hwui/Caches.h
index 804f609..e76df40 100644
--- a/libs/hwui/Caches.h
+++ b/libs/hwui/Caches.h
@@ -83,7 +83,7 @@
         return sInstance != nullptr;
     }
 private:
-    Caches(RenderState& renderState);
+    explicit Caches(RenderState& renderState);
     static Caches* sInstance;
 
 public: