Fix/suppress surfaceflinger google-explicit-constructor warnings

* Add explicit to conversion constructors/operators
* Use NOLINT or NOLINTNEXTLINE to suppress warnings on intended converters

Bug: 28341362
Test: make with WITH_TIDY=1 DEFAULT_GLOBAL_TIDY_CHECKS=-*,google-explicit-constructor
Change-Id: I8d88cf50fcef8a1ebeeececcb304828ab06d4788
diff --git a/services/surfaceflinger/DisplayHardware/ComposerHal.cpp b/services/surfaceflinger/DisplayHardware/ComposerHal.cpp
index 37ba433..f190b71 100644
--- a/services/surfaceflinger/DisplayHardware/ComposerHal.cpp
+++ b/services/surfaceflinger/DisplayHardware/ComposerHal.cpp
@@ -41,13 +41,12 @@
 
 class BufferHandle {
 public:
-    BufferHandle(const native_handle_t* buffer)
-    {
+    explicit BufferHandle(const native_handle_t* buffer) {
         // nullptr is not a valid handle to HIDL
         mHandle = (buffer) ? buffer : native_handle_init(mStorage, 0, 0);
     }
 
-    operator const hidl_handle&() const
+    operator const hidl_handle&() const // NOLINT(google-explicit-constructor)
     {
         return mHandle;
     }
@@ -81,7 +80,7 @@
         }
     }
 
-    operator const hidl_handle&() const
+    operator const hidl_handle&() const // NOLINT(google-explicit-constructor)
     {
         return mHandle;
     }