Added mouse down and enter events for columns and cells

[MrYogurt]

Added events for custom cells selecting in matrix case

[amanmahajan7]

Is this still needed? What is the use case of these events? Btw grid now supports onCellMouseDown
https://github.com/adazzle/react-data-grid/blob/main/src/DataGrid.tsx#L190

[CLAassistant]

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