Adding tests for all PennyLane transforms (#1215)

This PR adds unit tests for all PennyLane transforms. This PR addresses
[sc-72626].

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Co-authored-by: Ali Asadi <[email protected]>
Co-authored-by: David Ittah <[email protected]>
Co-authored-by: erick-xanadu <[email protected]>
Co-authored-by: soranjh <[email protected]>
Co-authored-by: Utkarsh <[email protected]>