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/ConfigDescription.h b/tools/aapt/ConfigDescription.h
index 4f999a2..09430f2 100644
--- a/tools/aapt/ConfigDescription.h
+++ b/tools/aapt/ConfigDescription.h
@@ -29,7 +29,7 @@
         size = sizeof(android::ResTable_config);
     }
 
-    ConfigDescription(const android::ResTable_config&o) {
+    ConfigDescription(const android::ResTable_config&o) {  // NOLINT(implicit)
         *static_cast<android::ResTable_config*>(this) = o;
         size = sizeof(android::ResTable_config);
     }