Refactor ownership cleanup and content slot management

[volynetstyle]

• Updated the addCleanup function to handle cleanup functions more efficiently by using a unified Cleanup type.
• Improved error handling in cleanup invocation with a dedicated invokeCleanup function.
• Simplified the runCleanups function to streamline cleanup execution and error reporting.
• Refactored the createContentSlot function to enhance clarity and reduce redundancy in state management.
• Introduced unmounting logic for current content in unmountCurrent to ensure proper cleanup of mounted nodes.
• Added tests for ownership lifecycle to verify the correct behavior of cleanup and disposal processes, including error handling during cleanup.
• Implemented a new runtime scheduler interface to manage flushing of reactive work and commit processes.
• Added performance benchmarks for various reactive scenarios to assess efficiency and responsiveness.