* Don't explicitly delete copy ctor of dynamic_format_arg_store
Explicitly deleting the copy ctor causes the move constructor to not be
implicitly generated. This behaviour is different than what was in
v8.0.1 and causes code that relied on the move ctor of
dynamic_format_arg_store to break.
* Add test for dynamic_format_arg_store's move ctor
* include <memory>, don't use make_unique
* all GTest/GMock files moved to `test/gtest` directory
* `CMakeLists.txt` created in `test/gtest` from `CMakeLists.txt` in `test`
* GTest/GMock target in CMake renamed to `gtest` (was `gmock`)
* CMake `gtest` target updated to export includes as "gtest/gtest.h" or "gmock/gmock.h" only
* includes in tests updated: "gtest.h" -> "gtest/gtest.h", "gmock.h" -> "gmock/gmock.h"
* removed duplications of `target_include_directories` for GTest/GMock directories (CMake manages them)
