vmTestbase/gc/g1/unloading/tests/unloading_compilation_level[1,2,3] time out without TieredCompilation

Not that much info in the test log, just a timeout information:

result: Error. Program `...jdk-16+28-2065/linux-aarch64-debug.jdk/jdk-16/fastdebug/bin/java' timed out (timeout set to 1200000ms, elapsed time including timeout handling was 1233561ms).

A thing to note: failed tests had `-XX:-TieredCompilation`, those with `-XX:+TieredCompilation` don't fail.

Have been seen only in Linux-aarch64-debug and Windows-x64-debug so far.