Add component memoization implementation plan

Two options for props-based memoization to skip re-renders:
- Option A: @ui.memo decorator (familiar to React devs)
- Option B: @ui.component(memo=True|compare_fn) parameter (cleaner)

Includes:
- API design and implementation details
- MemoizedFunctionElement and Renderer changes
- Unit tests for both options
- Performance benchmarks
- Comparison and recommendation (implement both)

Author: mofojed