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/aapt/FileFinder.cpp b/tools/aapt/FileFinder.cpp
index 18775c0..c9d0744 100644
--- a/tools/aapt/FileFinder.cpp
+++ b/tools/aapt/FileFinder.cpp
@@ -77,7 +77,7 @@
     return true;
 }
 
-void SystemFileFinder::checkAndAddFile(String8 path, const struct stat* stats,
+void SystemFileFinder::checkAndAddFile(const String8& path, const struct stat* stats,
                                        Vector<String8>& extensions,
                                        KeyedVector<String8,time_t>& fileStore)
 {