Revert "Revert "Remove `include/grpcpp/impl/codegen/client_callback.h` (#31005)" (#31079)" (#31087)

This reverts commit da08fe1d6f.

src/compiler/cpp_generator.cc

@@ -140,7 +140,7 @@ std::string GetHeaderIncludes(grpc_generator::File* file,
         "grpcpp/generic/async_generic_service.h",
         "grpcpp/support/async_stream.h",
         "grpcpp/support/async_unary_call.h",
-        "grpcpp/impl/codegen/client_callback.h",
+        "grpcpp/support/client_callback.h",
         "grpcpp/client_context.h",
         "grpcpp/impl/codegen/completion_queue.h",
         "grpcpp/impl/codegen/message_allocator.h",
@@ -1652,7 +1652,7 @@ std::string GetSourceIncludes(grpc_generator::File* file,
         "grpcpp/support/async_unary_call.h",
         "grpcpp/impl/codegen/channel_interface.h",
         "grpcpp/impl/codegen/client_unary_call.h",
-        "grpcpp/impl/codegen/client_callback.h",
+        "grpcpp/support/client_callback.h",
         "grpcpp/impl/codegen/message_allocator.h",
         "grpcpp/impl/codegen/method_handler.h",
         "grpcpp/impl/codegen/rpc_service_method.h",

test/cpp/codegen/compiler_test_golden

@@ -30,7 +30,7 @@
 #include <grpcpp/generic/async_generic_service.h>
 #include <grpcpp/support/async_stream.h>
 #include <grpcpp/support/async_unary_call.h>
-#include <grpcpp/impl/codegen/client_callback.h>
+#include <grpcpp/support/client_callback.h>
 #include <grpcpp/client_context.h>
 #include <grpcpp/impl/codegen/completion_queue.h>
 #include <grpcpp/impl/codegen/message_allocator.h>