Expose merge_cc_info from cc_info.bzl

Once this change is *released* in rules_cc and rules_java updated to use the new version, we can update rules_java/java/private/java_info.bzl, preventing that from widely-loading cc_common.

Compatibility mode loads native merge_cc_infos instead of the starlarked thing because when I tried forcing java_info to use cc_info.bzl's merge_cc_infos it failed on Bazel 8.

PiperOrigin-RevId: 876268175
Change-Id: Ib1d8b75da74c474c287ea6a485a6795515df0d41

cc/common/cc_info.bzl

diff --git a/cc/common/cc_info.bzl b/cc/common/cc_info.bzl
index 3370b54..c37f3de 100644
--- a/cc/common/cc_info.bzl
+++ b/cc/common/cc_info.bzl
@@ -13,6 +13,11 @@
 # limitations under the License.
 """CcInfo"""
 
-load("@cc_compatibility_proxy//:symbols.bzl", _CcInfo = "CcInfo")
+load(
+    "@cc_compatibility_proxy//:symbols.bzl",
+    _CcInfo = "CcInfo",
+    _merge_cc_infos = "merge_cc_infos",
+)
 
 CcInfo = _CcInfo
+merge_cc_infos = _merge_cc_infos

cc/extensions.bzl

diff --git a/cc/extensions.bzl b/cc/extensions.bzl
index 1daa70a..3cb5c75 100644
--- a/cc/extensions.bzl
+++ b/cc/extensions.bzl
@@ -93,7 +93,7 @@
             "symbols.bzl",
             """
 load("@rules_cc//cc/private:cc_common.bzl", _cc_common = "cc_common")
-load("@rules_cc//cc/private:cc_info.bzl", _CcInfo = "CcInfo")
+load("@rules_cc//cc/private:cc_info.bzl", _CcInfo = "CcInfo", _merge_cc_infos = "merge_cc_infos")
 load("@rules_cc//cc/private:cc_shared_library_info.bzl", _CcSharedLibraryInfo = "CcSharedLibraryInfo")
 load("@rules_cc//cc/private:debug_package_info.bzl", _DebugPackageInfo = "DebugPackageInfo")
 load("@rules_cc//cc/private:objc_info.bzl", _ObjcInfo = "ObjcInfo")
@@ -101,6 +101,7 @@
 
 cc_common = _cc_common
 CcInfo = _CcInfo
+merge_cc_infos = _merge_cc_infos
 DebugPackageInfo = _DebugPackageInfo
 CcToolchainConfigInfo = _CcToolchainConfigInfo
 ObjcInfo = _ObjcInfo
@@ -158,6 +159,7 @@
 load("@rules_cc//cc/private/rules_impl:native_providers.bzl", "NativeCcSharedLibraryInfo")
 cc_common = native_cc_common
 CcInfo = NativeCcInfo
+merge_cc_infos = cc_common.merge_cc_infos
 DebugPackageInfo = NativeDebugPackageInfo
 CcToolchainConfigInfo = NativeCcToolchainConfigInfo
 ObjcInfo = apple_common.Objc