Move __system_properties_reload to LIBC from LIBC_PLATFORM

The zygote cannot have visiblity to LIBC_PLATFORM methods. Therefore,
move __system_properties_reload to LIBC, and rename it
__system_properties_zygote_reload, and indicate in comments that it
should not be used by non-zygote apps

Bug: 291814949
Test: atest CtsBionicRootTestCases
Change-Id: Iee8fa0c76b740543c05a433393f2f4bef36d6d3d
diff --git a/tests/utils.cpp b/tests/utils.cpp
index 0c7c552..e123b42 100644
--- a/tests/utils.cpp
+++ b/tests/utils.cpp
@@ -89,6 +89,11 @@
   }
 }
 
+int64_t NanoTime() {
+  auto t = std::chrono::time_point_cast<std::chrono::nanoseconds>(std::chrono::steady_clock::now());
+  return t.time_since_epoch().count();
+}
+
 bool operator==(const Errno& lhs, const Errno& rhs) {
   return lhs.errno_ == rhs.errno_;
 }