[EuiDataGrid] Ensure gridStyles updates trigger a cell height recalculation

[mgadewoll]

Description

While working on this bugfix on EuiDataGrid we noticed that the gridStyles prop does not trigger a recalculation of cell heights.
While it's generally not expected to impact production (styles shouldn't change on the fly), it does show up in storybook and might create confusion that the grid does not update based on props as expected.

We should enable the fontSize and cellpadding props on gridStyles to be applied when changed.

Acceptance criteria

• gridstyles.fontSize and gridStyles.cellPadding trigger recalculation of EuiDataGrid cell heights (testable in Storybook via controls)