Fix/suppress aapt/aapt2 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: Ie02101ea7c422e8add535c111a30a2f21ead0ace
diff --git a/tools/aapt2/Debug.cpp b/tools/aapt2/Debug.cpp
index f064cb1..e0d7abe 100644
--- a/tools/aapt2/Debug.cpp
+++ b/tools/aapt2/Debug.cpp
@@ -414,7 +414,7 @@
  public:
   using xml::ConstVisitor::Visit;
 
-  XmlPrinter(Printer* printer) : printer_(printer) {
+  explicit XmlPrinter(Printer* printer) : printer_(printer) {
   }
 
   void Visit(const xml::Element* el) override {