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
* Use const reference type to avoid unnecessary copy.
Bug: 30413862
Test: build with WITH_TIDY=1

Change-Id: Id6d21961f313a1ad92b15a37fdaa5be9e8ab48e1
diff --git a/tools/aapt2/link/TableMerger.h b/tools/aapt2/link/TableMerger.h
index 6997f93..3473a27 100644
--- a/tools/aapt2/link/TableMerger.h
+++ b/tools/aapt2/link/TableMerger.h
@@ -115,7 +115,7 @@
                  const bool manglePackage,
                  const bool overlay,
                  const bool allowNewResources,
-                 FileMergeCallback callback);
+                 const FileMergeCallback& callback);
 
     std::unique_ptr<FileReference> cloneAndMangleFile(const std::string& package,
                                                       const FileReference& value);