fix: preserve custom layout falsy values

[fangsmile]

Summary

• merge collaborator branch biubiukam/fix/issue-1949-custom-layout-value onto latest develop
• preserve falsy cell values for custom layout and custom render callback args
• keep width/height computation and React custom layout update paths aligned with the same value passthrough

Notes

• recreated from collaborator PR fix: preserve custom layout falsy values #5196 on top of latest develop

Testing

• collaborator branch validation kept in original PR fix: preserve custom layout falsy values #5196

Closes #1949