Emits an AutoCloseable subclass declaration immediately before a try ARM block.
This is needed because AutoCloseable's close() method throws an exception
which we can't allow for compilation consistency so that means
we can't just create anonymous AutoCloseables in the try ARM clause.
We need to create anonymous ClRAutoCloseables.
We emit a new ClRAutoCloseables declaration (they are numbered across the instrumentation session)
for each try ARM block because the Clover instrumenter doesn't easily support
forward references to types we may inject.