Update CheckGCForNative for time based gc triggering.

Use the time based GC trigger threshold instead of growth_limit_ to make
sure we are doing GC in a timely manner in the case when small Java
objects hold on to large amounts of native memory.

Bug: 469141032
Test: manual inspection of perfetto traces
Flag: com.android.art.rw.flags.native_alloc_time_based_gc_triggering
Change-Id: Ic12c895232fcd247c14c310f622ab79abbdf392f