Use c10 version of half/bfloat16 in executorch

Pull Request resolved: #7040

Accomplished by importing relevant files from c10 into
executorch/runtime/core/portable_type/c10, and then using `using` in
the top-level ExecuTorch headers. This approach should keep the
ExecuTorch build hermetic for embedded use cases. In the future, we
should add a CI job to ensure the c10 files stay identical to the
PyTorch ones.
ghstack-source-id: 257038887
@exported-using-ghexport

Differential Revision: [D66106969](https://our.internmc.facebook.com/intern/diff/D66106969/)

Author: swolchok

.lintrunner.toml

@@ -78,6 +78,8 @@ exclude_patterns = [
     # File contains @generated
     'extension/llm/custom_ops/spinquant/fast_hadamard_transform_special.h',
     'extension/llm/custom_ops/spinquant/test/fast_hadamard_transform_special_unstrided_cpu.h',
+    # Want to be able to keep c10 in sync with PyTorch core.
+    'runtime/core/portable_type/c10/**',
 ]
 command = [
     'python',
@@ -261,6 +263,8 @@ exclude_patterns = [
     'extension/**',
     'kernels/optimized/**',
     'runtime/core/exec_aten/**',
+    # Want to be able to keep c10 in sync with PyTorch core.
+    'runtime/core/portable_type/c10/**',
     'runtime/executor/tensor_parser_aten.cpp',
     'scripts/**',
     'test/**',

CMakeLists.txt

@@ -356,7 +356,7 @@ if(NOT "${_repo_dir_name}" STREQUAL "executorch")
       "fix for this restriction."
   )
 endif()
-set(_common_include_directories ${CMAKE_CURRENT_SOURCE_DIR}/..)
+set(_common_include_directories ${CMAKE_CURRENT_SOURCE_DIR}/.. ${CMAKE_CURRENT_SOURCE_DIR}/runtime/core/portable_type)
 
 #
 # The `_<target>_srcs` lists are defined by including ${EXECUTORCH_SRCS_FILE}.
@@ -539,6 +539,7 @@ endif()
 target_include_directories(
   executorch_core PUBLIC ${_common_include_directories}
 )
+target_compile_definitions(executorch_core PUBLIC C10_USING_CUSTOM_GENERATED_MACROS)
 target_compile_options(executorch_core PUBLIC ${_common_compile_options})
 if(MAX_KERNEL_NUM)
   target_compile_definitions(
@@ -559,6 +560,7 @@ if(EXECUTORCH_BUILD_PYBIND AND APPLE)
   target_include_directories(
     executorch_core_shared PUBLIC ${_common_include_directories}
   )
+  target_compile_definitions(executorch_core_shared PUBLIC C10_USING_CUSTOM_GENERATED_MACROS)
   target_compile_options(
     executorch_core_shared PUBLIC ${_common_compile_options}
   )
@@ -579,6 +581,7 @@ endif()
 add_library(executorch ${_executorch__srcs})
 target_link_libraries(executorch PRIVATE executorch_core)
 target_include_directories(executorch PUBLIC ${_common_include_directories})
+target_compile_definitions(executorch PUBLIC C10_USING_CUSTOM_GENERATED_MACROS)
 target_compile_options(executorch PUBLIC ${_common_compile_options})
 target_link_options_shared_lib(executorch)
 
@@ -770,6 +773,8 @@ if(EXECUTORCH_BUILD_PYBIND)
   target_include_directories(
     util PUBLIC ${_common_include_directories} ${TORCH_INCLUDE_DIRS}
   )
+  target_compile_definitions(util PUBLIC C10_USING_CUSTOM_GENERATED_MACROS)
+
   target_compile_options(util PUBLIC ${_pybind_compile_options})
   target_link_libraries(util PRIVATE torch c10 executorch extension_tensor)