Add support for mouse event listeners on table row items

[peteharverson]

Add support for event listeners on table row items, for events such as onClick, onMouseEnter and onMouseLeave (https://reactjs.org/docs/events.html#mouse-events).

Currently they can be passed through to the table itself, for example:

      <EuiInMemoryTable
        items={this.props.tableData.anomalies}
        ...
        onMouseOver={this.onMouseOver}
      />

which allows you to detect onMouseOver somewhere on the table, but then something like jQuery needs to be used to traverse up and down the table DOM elements to find the table row item that has been clicked on.

It would be nice for example, if you could define e.g. onMouseOver on the table row items to allow for easy detection of the row that the event has been triggered on.