Fix/suppress startop google-explicit-constructor warnings

* Add explicit to conversion constructors/operators

Bug: 28341362
Test: make with WITH_TIDY=1 DEFAULT_GLOBAL_TIDY_CHECKS=-*,google-explicit-constructor
Change-Id: I9e7b929cfa65c68f4cdb4710c1c5c6760d56e4d5
2 files changed