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/libc/libc.map.txt b/libc/libc.map.txt
index d737946..156e9ee 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1600,6 +1600,7 @@
     tzalloc;
     tzfree;
     wcsrtombs_l;
+    __system_properties_zygote_reload; # apex
 } LIBC_U;
 
 LIBC_PRIVATE {
@@ -1806,7 +1807,6 @@
     __system_property_area_init;
     __system_property_set_filename;
     __system_property_update;
-    __system_properties_reload;
     android_fdsan_get_fd_table;
     android_fdtrack_compare_exchange_hook; # llndk
     android_fdtrack_get_enabled; # llndk