[Addition] [Low Priority] Add more unit tests for the fixed search space implementation

[ArlindKadra]

Add unit tests where we restrict the search space as follows:

• Skip Connections are disabled.
• Snapshot Ensembling is disabled.
• Weight Decay is disabled.
• Dropout is disabled.

Furthermore

• Restrictions for the network head.

All of the above were given errors and are now patched.

[ravinkohli]

This issue is now relevant for #358.