Change ArtStatsLog.write() to report unknown GC type

Bug: 249772734
Test: atest ArtGtestsTargetChroot
Merged-In: I5f0620fdcd9074f6f4896372dfb808c92affe425
Merged-In: I57bc9ae805c89df3b3713292742e6b3505f19d8e
Change-Id: I130e29377929b0703078acb1623b09b7651155d7
1 file changed