Delete Firestore public C++ API (#2050)

* Add firebase_cpp_sdk 5.4.0

... to the Firestore CMake build.

* Move C++ public API headers to cpp/include

* Add Firebase C++ API tests.

* Add support for building on Linux

* Add clang-format configuration for Firestore/cpp

* Add windows build support

* Review feedback

* Revert build changes to support Firebase C++ integration.

It turns out the public Firebase C++ SDK doesn't include enough to
actually build another component of that SDK externally so these changes
don't really help.

Eventually, once Firebase C++ is open source we'll integrate with that
to actually test Firestore's public C++ API.

* Delete Firestore/cpp and public C++ artifacts

It's not yet feasible to build these components externally so there's no
use in keeping them here.

Author: wilhuff

CMakeLists.txt

@@ -89,12 +89,12 @@ set(BUILD_TESTING ${old_build_testing} CACHE BOOL "Restore BUILD_TESTING" FORCE)
 
 
 # gRPC
-find_package(OpenSSL)
+find_package(OpenSSL QUIET)
 if(OPENSSL_FOUND)
   set(gRPC_SSL_PROVIDER package CACHE STRING "Use external OpenSSL")
 endif()
 
-find_package(ZLIB)
+find_package(ZLIB QUIET)
 if(ZLIB_FOUND)
   set(gRPC_ZLIB_PROVIDER package CACHE STRING "Use external ZLIB")
 endif()

Firestore/core/include/firebase/firestore/CMakeLists.txt

@@ -16,9 +16,6 @@
 # (see https://stackoverflow.com/questions/27039019/ and open issue on CMake
 # issue tracker: https://gitlab.kitware.com/cmake/cmake/issues/15234)
 add_custom_target(firebase_firestore_types_ide SOURCES
-    document_reference.h
-    event_listener.h
-    firestore.h
     firestore_errors.h
     geo_point.h
     timestamp.h