Use @pytorch// in bazel build files (#89660)

This change aims to make bazel build more embeeding-friendly.
Namely, when PyTorch is included as an external repo in another project, it is usually included like this
```
        native.local_repository(
            name = "pytorch",
            path = ...,
            repo_mapping = repo_mapping,
        )
```
Or
```
        http_archive(
            name = "pytorch",
            urls = ...
            repo_mapping = repo_mapping,
        )
```
In this case, references to `@//` would resolve to the top-level WORKSPACE that includes PyTorch.
That makes upgrades harder because we need to carry around this patch.
Note that under some edge-case circumstances even `//` resolves to the top-level `WORKSPACE`.

This change makes the embedding of the bazel build easier without compromising anything for the main repo, since the `@pytorch//` still refers to the same thing.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/89660
Approved by: https://github.com/kit1980

BUILD.bazel

@@ -2,11 +2,11 @@ load("@bazel_skylib//lib:paths.bzl", "paths")
 load("@pybind11_bazel//:build_defs.bzl", "pybind_extension")
 load("@rules_proto//proto:defs.bzl", "proto_library")
 load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_library", "cc_proto_library", "cc_test")
-load("//third_party:substitution.bzl", "header_template_rule")
-load("//:tools/bazel.bzl", "rules")
-load("//tools/rules:cu.bzl", "cu_library")
-load("//tools/config:defs.bzl", "if_cuda")
-load("//:aten.bzl", "intern_build_aten_ops", "generate_aten")
+load("@pytorch//third_party:substitution.bzl", "header_template_rule")
+load("@pytorch//:tools/bazel.bzl", "rules")
+load("@pytorch//tools/rules:cu.bzl", "cu_library")
+load("@pytorch//tools/config:defs.bzl", "if_cuda")
+load("@pytorch//:aten.bzl", "intern_build_aten_ops", "generate_aten")
 load(":build.bzl", "define_targets", "GENERATED_AUTOGRAD_CPP", "GENERATED_AUTOGRAD_PYTHON")
 load(":build_variables.bzl", "jit_core_sources", "libtorch_core_sources", "libtorch_cuda_sources", "libtorch_distributed_sources", "libtorch_extra_sources", "libtorch_nvfuser_generated_headers", "libtorch_nvfuser_runtime_sources", "libtorch_python_core_sources", "torch_cpp_srcs", "lazy_tensor_ts_sources")
 load(":ufunc_defs.bzl", "aten_ufunc_generated_cpu_sources", "aten_ufunc_generated_cpu_kernel_sources", "aten_ufunc_generated_cuda_sources")

third_party/gloo.BUILD

@@ -1,7 +1,7 @@
 load("@rules_cc//cc:defs.bzl", "cc_library")
-load("@//tools/rules:cu.bzl", "cu_library")
-load("@//third_party:substitution.bzl", "template_rule")
-load("@//tools/config:defs.bzl", "if_cuda")
+load("@pytorch//tools/rules:cu.bzl", "cu_library")
+load("@pytorch//third_party:substitution.bzl", "template_rule")
+load("@pytorch//tools/config:defs.bzl", "if_cuda")
 
 template_rule(
     name = "gloo_config_cmake_macros",

third_party/mkl-dnn.BUILD

@@ -1,5 +1,5 @@
 load("@rules_cc//cc:defs.bzl", "cc_library")
-load("@//third_party:substitution.bzl", "template_rule")
+load("@pytorch//third_party:substitution.bzl", "template_rule")
 
 _DNNL_RUNTIME_OMP = {
     "#cmakedefine DNNL_CPU_THREADING_RUNTIME DNNL_RUNTIME_${DNNL_CPU_THREADING_RUNTIME}": "#define DNNL_CPU_THREADING_RUNTIME DNNL_RUNTIME_OMP",
@@ -100,7 +100,7 @@ cc_library(
         "-fno-strict-overflow",
         "-fopenmp",
     ] + select({
-        "@//tools/config:thread_sanitizer": ["-DDNNL_CPU_RUNTIME=0"],
+        "@pytorch//tools/config:thread_sanitizer": ["-DDNNL_CPU_RUNTIME=0"],
         "//conditions:default": ["-DDNNL_CPU_RUNTIME=2"],
     }),
     includes = [
@@ -119,7 +119,7 @@ cc_library(
     deps = [
         "@mkl",
     ] + select({
-        "@//tools/config:thread_sanitizer": [],
+        "@pytorch//tools/config:thread_sanitizer": [],
         "//conditions:default": ["@tbb"],
     }),
 )

third_party/mkl.BUILD

@@ -13,7 +13,7 @@ cc_library(
         "libmkl_vml_avx512.so",
         "libmkl_vml_def.so",
     ] + select({
-        "@//tools/config:thread_sanitizer": [],
+        "@pytorch//tools/config:thread_sanitizer": [],
         "//conditions:default": ["libmkl_tbb_thread.so"],
     }),
     visibility = ["//visibility:public"],

third_party/sleef.BUILD

@@ -1,5 +1,5 @@
 load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_library")
-load("@//third_party:sleef.bzl", "sleef_cc_library")
+load("@pytorch//third_party:sleef.bzl", "sleef_cc_library")
 
 SLEEF_COPTS = [
     "-DHAVE_MALLOC_USABLE_SIZE=1",

third_party/tbb.BUILD

@@ -1,5 +1,5 @@
 load("@rules_cc//cc:defs.bzl", "cc_library")
-load("@//third_party:substitution.bzl", "template_rule")
+load("@pytorch//third_party:substitution.bzl", "template_rule")
 
 licenses(["notice"])  # Apache 2.0
 

third_party/tensorpipe.BUILD

@@ -1,5 +1,5 @@
 load("@rules_cc//cc:defs.bzl", "cc_library")
-load("@//third_party:substitution.bzl", "header_template_rule")
+load("@pytorch//third_party:substitution.bzl", "header_template_rule")
 
 LIBUV_COMMON_SRCS = [
     "third_party/libuv/src/fs-poll.c",