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/CacheUpdater.h b/tools/aapt/CacheUpdater.h
index 10a1bbc..6fa96d6 100644
--- a/tools/aapt/CacheUpdater.h
+++ b/tools/aapt/CacheUpdater.h
@@ -51,7 +51,7 @@
 class SystemCacheUpdater : public CacheUpdater {
 public:
     // Constructor to set bundle to pass to preProcessImage
-    SystemCacheUpdater (Bundle* b)
+    explicit SystemCacheUpdater (Bundle* b)
         : bundle(b) { };
 
     // Make sure all the directories along this path exist