Fix cucim dep compatibility

[wyli]

• update to use cucim>=21.8.2
• skip cucim related tests if not hasattr(cucim, "CuImage")
• use tifffile to create test cases instead of PIL

Status

Ready

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.