Swallow exception in gc_heap::fire_etw_allocation_event (#6571)

Swallow exception in gc_heap::fire_etw_allocation_event (#6571)

The gc_heap::fire_etw_allocation_event calls TypeHandle::GetName that can throw
due to OOM. But we don't want failures to fire event cause a failure during the GC,
so such exception should be swallowed and no event fired in such case.
This was discovered as a contract failure during test runs with ETW logging enabled
when this function was transitively called from Thread::PerformPreemptiveGC which
was recently modified to have NOTHROW contract.
Interestingly, this was not detected by the static contract checker.