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GH-39870: [Go] Include buffered pages in TotalBytesWritten (#40105)



### Rationale for this change

Currently, buffered data pages are not included in TotalBytesWritten this means that their is not an accurate estimate of the size of the current size. 

### Are there any user-facing changes?
`RowGroupTotalBytesWritten` will include the TotalBytes in buffered DataPages minus the buffered data pages headers. 

* Closes: #39870

Authored-by: Matthew McNew <me@mattmcnew.com>
Signed-off-by: Matt Topol <zotthewizard@gmail.com>