[Task]: Fix device and dtype

[SarahAlidoost]

Currently the device/dtype can be set in two places: ComputeConfig and EngineTestHelper(device=..., dtype=...). Here the changes required to address this issue:

• remove device/dtype from EngineTestHelper arguments
• make cpu default device
• fix notebooks regarding setting device
• fix notebooks regarding creating tensors inside the notebook, they should use the config values.
• see this comment.

See related comment.