Update GoogleTest used to 1.16.0 (#552)

Author: mcbarton

cmake/modules/GoogleTest.cmake

@@ -31,7 +31,7 @@ ExternalProject_Add(
   googletest
   GIT_REPOSITORY https://github.com/google/googletest.git
   GIT_SHALLOW 1
-  GIT_TAG v1.15.2
+  GIT_TAG v1.16.0
   UPDATE_COMMAND ""
   # # Force separate output paths for debug and release builds to allow easy
   # # identification of correct lib in subsequent TARGET_LINK_LIBRARIES commands