add finetune suite and update pre-training scripts

convlab/base_models/gpt/keyword_extraction/run.sh

...lab/base_models/gpt/keyword_extraction/test_t5_key2gen.sh

...ab/base_models/gpt/keyword_extraction/train_t5_key2gen.sh

convlab/base_models/gpt/keyword_extraction/train_t5_rg.sh

...t/keyword_extraction/train_t5_rg_key2gen+key2gen_noisy.sh

convlab/base_models/t5/key2gen/create_data.py

convlab/base_models/t5/key2gen/create_data_key2gen.py

convlab/base_models/t5/key2gen/dataset_vanilla.py

convlab/base_models/t5/key2gen/evaluate.py

convlab/base_models/t5/key2gen/features.py

convlab/base_models/t5/key2gen/finetune.sh

convlab/base_models/t5/key2gen/metric.py

convlab/base_models/t5/key2gen/run.sh

convlab/base_models/t5/key2gen/run2.sh

convlab/base_models/t5/key2gen/run_commongen.sh

convlab/base_models/t5/key2gen/run_commongen_key2gen.sh

convlab/base_models/t5/key2gen/run_dart.sh

convlab/base_models/t5/key2gen/run_dart_key2gen.sh

convlab/base_models/t5/key2gen/run_kvret.sh

convlab/base_models/t5/key2gen/run_kvret_fewshot.sh