[Lens] Allow hiding of columns in table

[flash1293]

Sometimes not all columns in a table should be shown initially if they are only important in some cases. To do so, it should be possible to configure a Lens table and hide certain columns.

Hiding columns should be implemented using the data grid toolbar (not part of the flyout) - the columns should not be sortable in here (we can implement this, but it would be a separate feature):

If there are hidden columns, the toolbar to show them is also shown on a dashboard, otherwise the toolbar is invisible on dashboards.

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)