[EuiDataGrid] cell actions are always rendered

[chandlerprall]

I believe this is a regression. Rendering cell actions requires creating multiple new elements per cell, times the visible cells, equals slower React&application performance especially as the grid is instantiating. The cell actions should not be included in the DOM unless they are [becoming] visible/interactive.

[chandlerprall]

Correction: cell actions are not rendered by default, but we don't clear the enableInteractions state after the mouse leaves the cell so they accumulate on the DOM.