Fixed device selection

[ambitious-octopus]

Pull Request Description:

This PR fixes issue #1189. This PR also allows better import of the set_working_device function, facilitating more effective DeviceManager singleton management.

Example Usage:

from model_compression_toolkit.core.pytorch import set_working_device

# Set the working device to 'GPU' or 'CPU'
set_working_device('GPU')

With this change, the set_working_device function can be easily imported and used to configure the DeviceManager's device context. This also allows a quantization to be tested on a specific device.

cc: @Idan-BenAmi

Checklist before requesting a review:

• I set the appropriate labels on the pull request.
• I have added/updated the release note draft (if necessary).
• I have updated the documentation to reflect my changes (if necessary).
• All function and files are well documented.
• All function and classes have type hints.
• There is a licenses in all file.
• The function and variable names are informative.
• I have checked for code duplications.
• I have added new unittest (if necessary).

[ambitious-octopus]

@Idan-BenAmi just FYI, I removed the additional import!

[Idan-BenAmi]

Hi @ambitious-octopus,
we've found the root cause of this issue (model.to() error), and we think #1204 is a better solution.