fix delegation in Piro::TrapezoidDecorator

Created by: ibaned

This decorator was deriving straight from Thyra::ModelEvaluatorDefaultBase and doing a lot of its own delegation, some of which was not quite right. Specifically, when delegating createInArgs and createOutArgsImpl, the argument object's model description needs to be changed, at least to comply with checks enabled when Teuchos_ENABLE_DEBUG=ON. Thyra has a base class ModelEvaluatorDelegatorBase specifically for creating decorators, so use that as the base class and let it provide most of the delegating methods.

This class seems to only be used by Albany, and this commit allows an Albany test to satisfy certain Thyra safety checks that it did not before.

@gahansen @agsalin @lxmota @bgranzow @mjuha