Protect grpc generated sources from unwanted system macros (grpc#39266)

grpc#38474 added protection from unwanted macros to the header files. This PR adds the same protection to the source files.
Without protection both in header and source files the code containing system macros will not compile. Macros will apply to function names in cc files and those will start to differ from the ones in header files.

This solves issues like described here: conda-forge/google-cloud-cpp-feedstock#196

Closes grpc#39266

COPYBARA_INTEGRATE_REVIEW=grpc#39266 from simia:protect_cc_files 3323fba
PiperOrigin-RevId: 751501020

Author: simia

src/compiler/cpp_generator.cc

@@ -1744,20 +1744,15 @@ std::string GetSourceIncludes(grpc_generator::File* file,
     auto printer = file->CreatePrinter(&output);
     std::map<std::string, std::string> vars;
     static const char* headers_strs[] = {
-        "functional",
-        "grpcpp/support/async_stream.h",
-        "grpcpp/support/async_unary_call.h",
-        "grpcpp/impl/channel_interface.h",
-        "grpcpp/impl/client_unary_call.h",
-        "grpcpp/support/client_callback.h",
-        "grpcpp/support/message_allocator.h",
-        "grpcpp/support/method_handler.h",
-        "grpcpp/impl/rpc_service_method.h",
-        "grpcpp/support/server_callback.h",
-        "grpcpp/impl/server_callback_handlers.h",
-        "grpcpp/server_context.h",
-        "grpcpp/impl/service_type.h",
-        "grpcpp/support/sync_stream.h"};
+        "functional", "grpcpp/support/async_stream.h",
+        "grpcpp/support/async_unary_call.h", "grpcpp/impl/channel_interface.h",
+        "grpcpp/impl/client_unary_call.h", "grpcpp/support/client_callback.h",
+        "grpcpp/support/message_allocator.h", "grpcpp/support/method_handler.h",
+        "grpcpp/impl/rpc_service_method.h", "grpcpp/support/server_callback.h",
+        "grpcpp/impl/server_callback_handlers.h", "grpcpp/server_context.h",
+        "grpcpp/impl/service_type.h", "grpcpp/support/sync_stream.h",
+        // ports_def.inc Must be included as last
+        "grpcpp/ports_def.inc"};
     std::vector<std::string> headers(headers_strs, array_end(headers_strs));
     PrintIncludes(printer.get(), headers, params.use_system_headers,
                   params.grpc_search_path);
@@ -2253,6 +2248,8 @@ std::string GetSourceEpilogue(grpc_generator::File* file,
       temp.append(*part);
       temp.append("\n");
     }
+    // Must be included at end of file
+    temp.append("#include <grpcpp/ports_undef.inc>\n");
     temp.append("\n");
   }