Fix mypy type errors in SanitySuite helper methods

[Copilot]

Helper methods in SanitySuite were accessing self._log which doesn't exist on the TestSuite base class, causing 8 mypy type errors.

Changes

• Added log parameter to helper methods: _is_marketplace_image() and _should_run_sanity() now accept the Logger instance passed from the test case
• Replaced self._log with log parameter: All logging calls now use the explicitly passed logger
• Fixed skip pattern: Replaced log.skip() (which doesn't exist on Logger) with raise SkippedException() following LISA's standard pattern

# Before
def _is_marketplace_image(self, node: Node) -> bool:
    self._log.debug("...")  # Error: _log doesn't exist

# After  
def _is_marketplace_image(self, log: "Logger", node: Node) -> bool:
    log.debug("...")  # Uses passed logger

All 526 source files now pass mypy strict type checking.

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