Moving things out of CharRow into ROW helps us hide it as an implementation detail.
This is part one of many.
### CharRow: Hide ClearCell, use ROW::ClearColumn
### CharRow: Hide GetText, use ROW::GetText
### CharRowBaseTests: remove dead file (never used!)
### CharRow: Move DoubleBytePadded into ROW
### CharRow: Move WrapForced into ROW
### Char/AttrRow: Hide Reset, use ROW::Reset
### Remove RowCellIterator (dead code)
RCI was unused; it was replaced by TextBufferCellIterator shortly after its creation
### Move AttrRowTests to ut_textbuffer from ut_host
It had no reliance on the host.
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