transformers

1c8c2d9a - [WIP][examples/seq2seq] move old s2s scripts to legacy (#10136)

[WIP][examples/seq2seq] move old s2s scripts to legacy (#10136) * move old s2s scripts to legacy * add the tests back * proper rename * restore * Apply suggestions from code review Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com> Co-authored-by: Stas Bekman <stas@stason.org> Co-authored-by: Stas Bekman <stas00@users.noreply.github.com> Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>