Fix linting errors in autoscale code

- Add missing getpass import in salt/crypt.py
- Remove duplicate PublicKey class definition
- Add pylint disable comments for intentional super().__init__() overrides
- Remove unused shutil import from salt/channel/server.py
- Add explicit utf-8 encoding to pathlib.Path().write_text() calls
- Add pylint disable comments for intentional broad exception handlers
- Fix test imports to use tests.support.mock instead of unittest.mock
- Remove unused hashlib import from integration test

All linting now passes with 10/10 rating.

Author: dwoz