refactor: migrate C++ runfiles API from bazel_tools to rules_cc

Bazel 9 moves the C++ runfiles library from @bazel_tools to @rules_cc.
Update zipmerge_test.cpp:
- Change include from tools/cpp/runfiles to rules_cc/cc/runfiles
- Update namespace from bazel::tools::cpp::runfiles to rules_cc::cc::runfiles

Note: The BUILD.bazel dependency change is in a separate commit.

Author: redsun82

misc/bazel/internal/zipmerge/zipmerge_test.cpp

@@ -9,9 +9,9 @@
 
 #include <gtest/gtest.h>
 #include <gmock/gmock.h>
-#include "tools/cpp/runfiles/runfiles.h"
+#include "rules_cc/cc/runfiles/runfiles.h"
 
-using bazel::tools::cpp::runfiles::Runfiles;
+using rules_cc::cc::runfiles::Runfiles;
 using namespace std::string_literals;
 namespace fs = std::filesystem;