[Blocking] Emulate the unpack and pack on vectors using insert_strided_slice and extract_strided_slice

[chencha3]

This PR replaces unpack op for Vectors with insert_strided_slice
and pack op for vectors with extract_strided_slice. This would have
some performance penalty for a few tests, but matchs the upstream
implementation, and we can reuse patterns from upstream for, e.g., vectorizable ops

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