Fix buildifier warnings in @rules_cc

Fixes:

* Enabled buildifier on the Bazel CI again
* Added Skydocs where missing
* Moved public files out of .../private/... (e.g. cc_toolchain_config_lib.bzl)
* Reformatted
* Removed unused loads
* Using relative labels for cc_configure related files
* Added development dependency on rules_proto
    * they're not in the federation yet, so hand rolling in rules_cc's WORKSPACE file
* Added development dependency on rules_python (from federation)
* Cleaned up copybara (notable change - not using @rules_cc in labels inside rules_cc repo)
* Made cc_flags_supplier usable internally
* Moved load statements to the top of the bzl file
* Moved runfiles to the tools directory
* Unified toolchain_utils.bzl and find_cc_toolchain.bzl

RELNOTES: None.
PiperOrigin-RevId: 276479521

tools/cpp/BUILD.empty

@@ -35,8 +35,6 @@ cc_toolchain_suite(
 
 cc_toolchain(
     name = "local",
-    toolchain_identifier = "local",
-    toolchain_config = ":local_config",
     all_files = ":empty",
     ar_files = ":empty",
     as_files = ":empty",
@@ -45,6 +43,8 @@ cc_toolchain(
     linker_files = ":empty",
     objcopy_files = ":empty",
     strip_files = ":empty",
+    toolchain_config = ":local_config",
+    toolchain_identifier = "local",
 )
 
 cc_toolchain_config(name = "local_config")

tools/cpp/BUILD.static.freebsd

@@ -41,8 +41,6 @@ cc_toolchain_suite(
 
 cc_toolchain(
     name = "cc-compiler-freebsd",
-    toolchain_identifier = "local_freebsd",
-    toolchain_config = ":local_freebsd",
     all_files = ":empty",
     ar_files = ":empty",
     as_files = ":empty",
@@ -52,6 +50,8 @@ cc_toolchain(
     objcopy_files = ":empty",
     strip_files = ":empty",
     supports_param_files = 0,
+    toolchain_config = ":local_freebsd",
+    toolchain_identifier = "local_freebsd",
 )
 
 cc_toolchain_config(
@@ -75,8 +75,6 @@ toolchain(
 
 cc_toolchain(
     name = "cc-compiler-armeabi-v7a",
-    toolchain_identifier = "stub_armeabi-v7a",
-    toolchain_config = ":stub_armeabi-v7a",
     all_files = ":empty",
     ar_files = ":empty",
     as_files = ":empty",
@@ -86,6 +84,8 @@ cc_toolchain(
     objcopy_files = ":empty",
     strip_files = ":empty",
     supports_param_files = 0,
+    toolchain_config = ":stub_armeabi-v7a",
+    toolchain_identifier = "stub_armeabi-v7a",
 )
 
 cc_toolchain_config(

tools/cpp/BUILD.toolchains.tpl

@@ -1,4 +1,5 @@
 load("@local_config_platform//:constraints.bzl", "HOST_CONSTRAINTS")
+
 toolchain(
     name = "cc-toolchain-%{name}",
     exec_compatible_with = HOST_CONSTRAINTS,
@@ -17,4 +18,3 @@ toolchain(
     toolchain = "@local_config_cc//:cc-compiler-armeabi-v7a",
     toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
 )
-

tools/cpp/osx_cc_configure.bzl

@@ -24,7 +24,6 @@ load(
 load(
     "@bazel_tools//tools/cpp:unix_cc_configure.bzl",
     "configure_unix_toolchain",
-    "find_cc",
     "get_env",
     "get_escaped_cxx_inc_directories",
 )