Standardize conv len function for audio models

[diegoakel]

What does this PR do?

Standardize conv len function for audio models, uses the following implementation:

def _conv_out_length(input_length, kernel_size, stride, pad=0, dilation=1):
    # 1D convolutional layer output length formula taken
    # from https://pytorch.org/docs/stable/generated/torch.nn.Conv1d.html
    return torch.div(input_length + 2 * pad - dilation * (kernel_size - 1) - 1, stride, rounding_mode="floor") + 1

Fixes #42118

Before submitting

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Who can review?

@eustlb

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: data2vec, hubert, seamless_m4t, seamless_m4t_v2, sew, sew_d, speecht5, unispeech, unispeech_sat, wav2vec2, wav2vec2_bert, wav2vec2_conformer, wavlm