Add multilingual translation serving

[jonatanklosko]

Adds a translation serving. It builds on top of text generation serving, but the serving input expects a source and target language to be specified alongside the text. The language is configured as part of input, so that the same serving can be used for different language pairs.

repository_id = "facebook/nllb-200-distilled-600M"

{:ok, model_info} = Bumblebee.load_model({:hf, repository_id})
{:ok, tokenizer} = Bumblebee.load_tokenizer({:hf, repository_id})
{:ok, generation_config} = Bumblebee.load_generation_config({:hf, repository_id})

serving = Bumblebee.Text.translation(model_info, tokenizer, generation_config)

text = "The bank of the river is beautiful in spring"

Nx.Serving.run(serving, %{
  text: text,
  source_language_token: "eng_Latn",
  target_language_token: "pol_Latn"
})
#=> %{
#=>   results: [
#=>     %{
#=>       text: "W wiosnę brzeg rzeki jest piękny",
#=>       token_summary: %{input: 11, output: 13, padding: 0}
#=>     }
#=>   ]
#=> }