transformers

de4d71ea - Removed Bert dependency from BertGeneration code base. (#19370)

Removed Bert dependency from BertGeneration code base. (#19370) * Copied all the code required from transformers.models.bert.modeling_bert to here * Fixed styling issues * Reformatted copied names with Model specific name. * Reverted BertEncoder part as there is already a class called BertGenerationEncoder * Added prefixes in missing places. Co-authored-by: vishwaspai <vishwas.pai@emplay.net>