fdsan: expose functions to get and interpret tags.

Make it easier to write tests in users of fdsan by exposing functions
to allow users to get and interpret the tags.

Test: bionic_unit_tests
Change-Id: Iafa9bcaeb5e4db230f3dfec6f483274f34602694
diff --git a/libc/libc.arm64.map b/libc/libc.arm64.map
index 1cf48b1..4d538cd 100644
--- a/libc/libc.arm64.map
+++ b/libc/libc.arm64.map
@@ -1347,6 +1347,9 @@
     android_fdsan_close_with_tag;
     android_fdsan_create_owner_tag;
     android_fdsan_exchange_owner_tag;
+    android_fdsan_get_owner_tag;
+    android_fdsan_get_tag_type;
+    android_fdsan_get_tag_value;
     android_fdsan_get_error_level;
     android_fdsan_set_error_level;
     timespec_get;