Update _header_modules_feature in cc_toolchain_config.bzl to match prod crosstool behavior.

Update _header_modules_feature so that header_modules implies header_module_compile and requires use_header_modules (rather than implying use_header_modules), matching the prod crosstool configuration. Enable _use_header_modules_feature by default and register FEATURE_NAMES.use_header_modules in the features dictionary.

BEGIN_PUBLIC
Update _header_modules_feature in cc_toolchain_config.bzl to match prod crosstool behavior.
END_PUBLIC

#proto_library_starlark_migration

PiperOrigin-RevId: 966674919
Change-Id: Iad67e50ee41b3323f0ab770f85475d0ff5a3335c

tests/cc/testutil/toolchains/cc_toolchain_config.bzl

diff --git a/tests/cc/testutil/toolchains/cc_toolchain_config.bzl b/tests/cc/testutil/toolchains/cc_toolchain_config.bzl
index f712751..50fefe6 100644
--- a/tests/cc/testutil/toolchains/cc_toolchain_config.bzl
+++ b/tests/cc/testutil/toolchains/cc_toolchain_config.bzl
@@ -157,7 +157,8 @@
 
 _header_modules_feature = feature(
     name = FEATURE_NAMES.header_modules,
-    implies = ["use_header_modules", "header_module_compile"],
+    implies = ["header_module_compile"],
+    requires = [feature_set(features = ["use_header_modules"])],
 )
 
 _header_module_compile_feature = feature(
@@ -216,6 +217,7 @@
 
 _use_header_modules_feature = feature(
     name = FEATURE_NAMES.use_header_modules,
+    enabled = True,
     flag_sets = [
         flag_set(
             actions = [
@@ -1798,6 +1800,7 @@
     FEATURE_NAMES.compiler_param_file: _compiler_param_file_feature,
     FEATURE_NAMES.gcc_quoting_for_param_files: _gcc_quoting_for_param_files_feature,
     FEATURE_NAMES.module_maps: _module_maps_feature,
+    FEATURE_NAMES.use_header_modules: _use_header_modules_feature,
     FEATURE_NAMES.static_link_cpp_runtimes: _static_link_cpp_runtimes_feature,
     FEATURE_NAMES.simple_compile_feature: _simple_compile_feature,
     FEATURE_NAMES.simple_link_feature: _simple_link_feature,