🧪 test: add unit tests for orientation setter

[Dor-bl]

🎯 What: The orientation setter lacked test coverage in the Appium Python Client, and also silently skipped invalid orientation values instead of raising an error.
📊 Coverage: The new tests in test/unit/webdriver/webdriver_test.py cover:

• Getting the orientation
• Setting valid orientations ('LANDSCAPE', 'PORTRAIT')
• Setting invalid orientations (e.g. 'INVALID'), checking that a WebDriverException is correctly raised
  ✨ Result: Test coverage for the orientation property is complete, and the underlying implementation is more robust as it throws a proper error for incorrect orientations.

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PR created automatically by Jules for task 7851551434230814572 started by @Dor-bl

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