Fix batching in fairseq SentencepieceTokenizer

[Craigacp]

This fixes #639 by moving the fairseq id patching out of the loop so it's not applied multiple times to sequences earlier in the batch.

I've added the check to ensure it's not applied when add_rev is true mirroring its position in the for loop, but I'm unsure if that's required (presumably there are no HF tokenizers which emit a reversed string and have this fairseq hack?).

I tested it against the example in #639 and both batches and single sequences work correctly now.

[wenbingl]

/azp run onnxruntime-extensions.CI

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[wenbingl]

/azp run onnxruntime-extensions.CI

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[Craigacp]

I ran the Python tests locally on macOS ARM64 and everything passed. The access violation in the Windows tests happens either in test_cliptok or test_cv2 both of which passed fine on my machine and don't use the code I changed, and they also passed fine in Linux and macOS in the CI. Is there anything more I can do to run the failure down?

[wenbingl]

@sayanshaw24 , can you review this PR?

[sayanshaw24]

good catch! missed the !add_rev check in the if-statement - this looks good, thanks for this.