Fix OV model for BLOOM architecture

[echarlaix]

In this PR we patch the model before the ONNX / OpenVINO export for both bloom and llama architecture in order to fix the decoder mask generation.
Fix #327

cc @sammysun0711 @usstq

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[eaidova]

@echarlaix I believe this fix is not complete. function which you patch for llama model, can be also find in other model types e.g. blenderbot and opt, so I assume that more models can be affected here.

[echarlaix]

Hi @eaidova ! Sure let me check it right now and add a fix ! Currently, here are the models architectures we are officially supporting, it could make sense to disable or at least add a warning when exporting other architectures.