Fix google-explicit-constructor warnings in system/core.

* Declare explicit conversion constructors.
* Add NOLINT for implicit conversion constructors.
* Fix also some misaligned indendations.

Bug: 28341362
Change-Id: Idf911f35923b408d92285cc1a053f382ba08c63e
Test: build with clang-tidy
diff --git a/logd/LogBuffer.h b/logd/LogBuffer.h
index b390a0c..162c189 100644
--- a/logd/LogBuffer.h
+++ b/logd/LogBuffer.h
@@ -103,7 +103,7 @@
 public:
     LastLogTimes &mTimes;
 
-    LogBuffer(LastLogTimes *times);
+    explicit LogBuffer(LastLogTimes *times);
     void init();
     bool isMonotonic() { return monotonic; }