Use C++'s smart pointers std::unique_ptr and std::shared_ptr instead of our own. (#1365)

* Remove headers from CMake file.

* Find-and-replace change.

* Format code.

* Find and replace for std::atomic.

* Format code.

* Update to Dec 2022 release of boringssl.

In this release, the "src" directory is removed from boringssl,
so there are some CMake and patch changes necessary for compatibility.

* Re-add patch file.

* Switch to std::make_unique.

* Fix make_shared, std::move, and class initialization.

* WIP.

* Fix more move syntax.

* Fix more std::move issues.

Revert Firestore.

* Remove debug output

* Fix Android Firestore test, and Storage assignment.

* Make the callback safer via shared_ptr.

* Fix lint errors.

* Format code.

* More lint fixes.

* More lint.

* Additional lint warning fixes.

* Fix Firestore test.

* Fix more lints.

* Lint lint lint.

* Change RequestDataPtr to a unique_ptr since STLPort is no longer used.

* Remove Move() and Forward(), replacing with std::move() and std::foward<>().

* Format code and lint fixes.

* Change firebase::Move explicitly to std::move.

* Remove lint warnings for headers.

* More lint warnings on includes.

* Format code.

* Return back to shared pointer.

* Add note about NewCallback and link to TODO.

* Fix lint error.

* Fix a lingering firebase::Move.

* Fix optional_test to mock Move correctly again.

* Revert prereqs script, python3 change will be made elsewhere.

* Lint.

* Remove references to atomic_test.

* Fix Move -> std::move once more

* Fix a seg fault race condition on Linux by using a unique_ptr.

This code always wanted to use a unique_ptr, but was previously
using a SharedPtr because of STLPort.

However, even without STLPort, there is still an issue switching
it to a unique_ptr, which is that std::priority_queue is misdesigned
and does not return a mutable reference in C++14.

Because of this, if we want to std::move from a priority queue,
we need to do a const cast.

* Empty commit.

* Fix test error.

* Fix test compilation error.

* Fix additional test build error.

* Vector initializer lists use copy semantics. Switch to push_back since these are just tests.

* Fix Forward --> std::forward from the merged Firestore change.

* Add callback tests for shared_ptr wrapping a unique_ptr.

Author: jonsimantov

app/CMakeLists.txt

@@ -59,7 +59,7 @@ set(FLATBUFFERS_FLATC_SCHEMA_EXTRA_ARGS
     "--no-union-value-namespacing"
     "--gen-generated"
     "--gen-object-api"
-    "--cpp-ptr-type" "flatbuffers::unique_ptr")
+    "--cpp-ptr-type" "std::unique_ptr")
 # Because of a bug in the version of Flatbuffers we are pinned to,
 # additional flags need to be set.
 set(FLATC_ARGS "${FLATBUFFERS_FLATC_SCHEMA_EXTRA_ARGS}")
@@ -180,7 +180,7 @@ set(FLATBUFFERS_FLATC_SCHEMA_EXTRA_ARGS
     "--no-union-value-namespacing"
     "--gen-generated"
     "--gen-object-api"
-    "--cpp-ptr-type" "flatbuffers::unique_ptr")
+    "--cpp-ptr-type" "std::unique_ptr")
 # Because of a bug in the version of Flatbuffers we are pinned to,
 # additional flags need to be set.
 # also see if app_generated_includes will conflict
@@ -351,10 +351,6 @@ add_library(firebase_app STATIC
     ${utility_HDRS}
     ${app_platform_HDRS}
     ${FIREBASE_GEN_FILE_DIR}/app/google_services_generated.h
-    memory/atomic.h
-    meta/move.h
-    memory/unique_ptr.h
-    memory/shared_ptr.h
     ${app_flatbuffers_srcs})
 
 set_property(TARGET firebase_app PROPERTY FOLDER "Firebase Cpp")