Fix clang-tidy warnings in aapt and aapt2.

* Add explicit keyword to conversion constructors.
* Add NOLINT(implicit) comments for implicit conversion constructors.
Bug: 28341362
* Use const reference type for read-only parameters.
Bug: 30407689
* Add NOLINT to suppress wrong clang-tidy warnings on macros.
Test: build with WITH_TIDY=1

Change-Id: Ibfafb23d9be463b4072745a51a6d9f1812dcac45
diff --git a/tools/aapt2/Source.h b/tools/aapt2/Source.h
index 319528e..8a1021d 100644
--- a/tools/aapt2/Source.h
+++ b/tools/aapt2/Source.h
@@ -35,7 +35,7 @@
 
     Source() = default;
 
-    inline Source(const StringPiece& path) : path(path.toString()) {
+    inline Source(const StringPiece& path) : path(path.toString()) {  // NOLINT(implicit)
     }
 
     inline Source(const StringPiece& path, size_t line) : path(path.toString()), line(line) {