Created by: wojtuss

This PR adds support for the Ernie NLP model in QAT2.0. A documentation update explaining how to run accuracy and performance benchmarks on this model is submitted in a separate PR: https://github.com/PaddlePaddle/Paddle/pull/22519. For the performance benchmark to work, the PR https://github.com/PaddlePaddle/benchmark/pull/311 needs to be merged.