patch: backports module availability for transformers<4.18

[aarnphm]

What does this PR address?

Patching the available check for transformers 4.18

Signed-off-by: Aaron 29749331+aarnphm@users.noreply.github.com

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[larme]

LGTM in general. Just want to make sure signatures inference will be disabled is for version less than 4.17. And is_tf_available etc. is not available for version less than 4.18. Is that right? Because these 2 versions are so close.

[aarnphm]

Oh no, the signature here are since processing_utils only available since 4.18