performance issue in spatial profile generation along a line or a polyline

[kswang1029]

as of v4-stable, the spatial profiler generation process along a line or a polyline is not that performant. The impact to users is they will need to wait a while before seeing the results. If performance cannot be improved significantly, we will need to implement "progressive update + cancellation" similar to the region spectral profiler (CARTAvis/carta-frontend#1954 + #1179).

[pford]

Related issue #1347, refactoring Region class for better performance using reference image.