Make all class redefinition operations after suspend_all infallible

We can guarantee that the mutations to the class, classloader, method
& stack data-structures which occur after the suspend_all can never
fail. This will simplify implementing the required semantics of class
redefinition with respect to atomically updating multiple classes at
once.

Test: mma -j40 test-art-host
Change-Id: Iab95c66afbdcfe161a9486f5fb7193c53642c060