feat(DataTable): add batch actions select all button addition

[matthewgallo]

Closes #12595

This PR adds a Select all button to the TableBatchActions component if onSelectAll is passed to the component. The actual select all logic will be handled by the consumer as discussed in #12595. The main purpose of this addition is so that we can implement the following in the batch action toolbar in Carbon for IBM Products Datagrid:

Changelog

New

• Added onSelectAll and totalCount properties to TableBatchActions
• Added test to validate that onSelectAll is called as expected

Changed

• I also noticed two small prop type errors that I fixed, relating to button sizes, changing small to sm in the batch action stories.

Testing / Reviewing

I have added these two new props to one of the DataTable batch action stories to view as an example and added an additional test to validate that onSelectAll is called appropriately.

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[guidari]

Thanks for adding this! 🚀