[EuiInMemoryTable] Support same Pagination props as EuiBasicTable

[chrisronline]

The EuiBasicTable supports multiple pagination options that are not supported in the EuiInMemoryTable

We should aim for parity here unless there is a strong reason for something to only exist in one.

[chandlerprall]

I don't think this needs to be a breaking change; EuiInMemoryTable doesn't need to expose totalItemCount as it already tracks items, and it exchanges pageSize for initialPageSize - the only prop that is missing is pageIndex/initialPageIndex.

[igoristic]

You're right, for some reason I assumed that EuiBasicTable prop names are actually index and size instead of pageIndex and pageSize. And, that this improvement will be to make the names consistent

[chandlerprall]

#4038 introduced pageIndex & pageSize values to EuiInMemoryTable's pagination prop, further aligning on pagination value names & support. I feel the basic & in-memory paginations have been aligned enough to close this out, feel free to re-open with more details if something is missing.