ART: Rewrite Runtime fault message to be lock-free

To avoid the lock in a general header, rewrite the fault message
(that is almost unused) to be lock-free. Store the string as a
heap object owned by Runtime.

Bug: 119869270
Test: mmma art
Test: m test-art-host
Change-Id: Ib1e027a1543c46d25953119f05792f0e874d6a3d