Fix/suppress libs/vr 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: I3631041531e3fb5cbcee246a7e7bb94fb06aa60b
diff --git a/services/vr/virtual_touchpad/VirtualTouchpadService.h b/services/vr/virtual_touchpad/VirtualTouchpadService.h
index 2c46209..2c88aec 100644
--- a/services/vr/virtual_touchpad/VirtualTouchpadService.h
+++ b/services/vr/virtual_touchpad/VirtualTouchpadService.h
@@ -13,7 +13,7 @@
 //
 class VirtualTouchpadService : public BnVirtualTouchpadService {
  public:
-  VirtualTouchpadService(std::unique_ptr<VirtualTouchpad> touchpad)
+  explicit VirtualTouchpadService(std::unique_ptr<VirtualTouchpad> touchpad)
       : touchpad_(std::move(touchpad)), client_pid_(0) {}
   ~VirtualTouchpadService() override;