Correct exception behavior for default methods

Default methods are defined to throw an IncompatibleClassChangeError
(ICCE) when they are called and there is no "best" implementation.
Previously we would simply throw an ICCE during class loading as soon
as we noticed that this would happen if called. This makes us wait
until we actually attempt to execute the method. Furthermore, this
allows us to use other, non-conflicting, methods on the object as
normal.

Furthermore, this makes us correctly throw AbstractMethodErrors in
cases where all default implementations of a method are overridden by
abstract declarations.

Adds 3 tests for this new behavior.

Bug: 24618811

Change-Id: Id891958a81f9b3862b2ce5919636aabef7d3422e