add gpt2 model for the paddlenlp

* update docs

* support AMP training

* add pure fp16 training.

* Add lookup_table in custom_black_list during the pure fp16 training.

* add static predict

* rm position_encoding_init

* fix static predict

* add the xpu support the the paddlenlp

* add the support xpu for the ernie and bert
Co-authored-by: Nwawltor <fanzeyang0904@hotmail.com>

* add ernie_gen

* optimize ernie_gen

* optimize ernie_gen

* optimize ernie_gen code

* fix crf bug

* add ernie_gen __init__.py

* modify nlp version

* fix ernie_gen predict

add ernie_gen for the dygraph mode

update codes for paddenlp text cls example

* add paddle.models api reference docs

* update docs

* update docs

* optimize lac

* formatted

* optimize lac

* optimize lac

* Add TokenEmbedding

* download corpus embedding data
* load embedding data by specifying corpus name
* extend the vocab of tokenizer from corpus embedding data

* add unk token setting

* modify tokenizer

* add extend voacb

* move jieba tokenizer and rename corpus_name->embedding_name

* use bos url instead of localhost

* add log when loading data

* add token dot computation; add __repr__ of TokenEmbedding

* add color logging

* use paddlenlp.utils.log

* adjust repr

* update pretrained embedding table

* fix padding idx

* add electra pretrain and modify style of electra modeling

* add electra pretrain, modify style of electra modeling and fix problems of review

* delete predict_classifer

* modify accu to acc

* add paddlenlp.metrics.glue

use paddlenlp downloader for the tokenizer

* add model api

* update codes

* update codes

* update codes