Support >4GB strings in the TorchScript model (#99104)
Summary: The support of BINUNICODE8 is missing. So adding it. So we can support attributes > 4GB. For example, for very large model, we save the lowered model in the EngineHolder using a string attribute.
Test Plan: buck2 test mode/opt //caffe2/test:jit -- --exact 'caffe2/test:jit - test_save_load_large_string_attribute (jit.test_save_load.TestSaveLoad)'
Differential Revision: D44905770
Pull Request resolved: https://github.com/pytorch/pytorch/pull/99104
Approved by: https://github.com/qihqi
