[py] Implement __hash__ and explicit ScriptKey equality comparison - #18243

Description

ScriptKey is used in the Python bindings as an identifier for pinned scripts (driver.pin_script(), driver.unpin()).

Previously:

1. ScriptKey defined __eq__ without defining __hash__, which in Python 3 implicitly sets __hash__ = None. Attempting to use a ScriptKey in a dictionary or set raised TypeError: unhashable type: 'ScriptKey'.
2. __eq__ compared self._id == other directly without checking whether other is an instance of ScriptKey or a raw ID, relying on reflected equality for ScriptKey == ScriptKey.

This PR:

• Implements __hash__ returning hash(self._id) so ScriptKey instances can be hashed and stored in sets or mappings.
• Compares self._id == other._id when other is an instance of ScriptKey, while preserving raw ID comparisons.
• Adds comprehensive unit tests in py/test/unit/selenium/webdriver/remote/script_key_tests.py.

Motivation and Context

Enables using \ScriptKey\ objects as keys in hash mappings/sets and resolves Ruff warning \PLW1641.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.