BUG #14809: Use title size when placing title in vtkChartXY.
vtkChartXY did not use the space used by the title text and top-axes to determine where to place the title text. That resulted in cases where the title overlapped the top-axes labels or for larger font sizes, simply didn't have enough room. Fixed that by ensuring that the title placement/border determination code uses the title text's size. Updated TestLinePlotAxisFonts test to test this new functionality. Change-Id: Idac42b970eb27ebbaee95adf43748d79747cd1dc