What does this PR do? Please describe:
This PR builds upon #740 by integration huggingface ASR models with the hg evaluation CLI interface. I have added ModelConfig and utilized hydra-core to dynamically load the relevant classes.

Note: This PR depends on some changes that were made in #749. This PR's contributions starts from this commit d80d154

for Example:

• Loading whisper model:

$ fairseq2 hg asr /tmp/fairseq2 --config max_samples=2 model_config.model_name=openai/whisper-tiny.en model_config.dtype=torch.float32 model_config.model_class=WhisperForConditionalGeneration model_config.tokenizer_class=WhisperProcessor model_config.tokenizer_name=openai/whisper-tiny.en 

...
[08/16/24 20:28:09] INFO     fairseq2.recipes.hg.evaluator - Eval Metrics - BLEU: 0.577036 | Elapsed Time: 1s | Wall Time: 2s | brevity_penalty: 1.0 | length_ratio: 1.15 | precisions:
                             [0.7391304347826086, 0.6363636363636364, 0.5238095238095238, 0.45] | reference_length: 40 | translation_length: 46                                        
                    INFO     fairseq2.recipes.hg.evaluator - Evaluation complete in 2 seconds                                                                                          

Does your PR introduce any breaking changes? If yes, please list them:
None.

Check list:

• Was the content of this PR discussed and approved via a GitHub issue? (no need for typos or documentation improvements)
• Did you read the contributor guideline?
• Did you make sure that your PR does only one thing instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests?
• Did you verify new and existing tests pass locally with your changes?
• Did you update the CHANGELOG? (no need for typos, documentation, or minor internal changes)