performance issue in region spectral profile generation

[kswang1029]

Based on the internal face-to-face meeting in 2023 Nov, there appears room for performance improvement in region spectral profile generation. This performance issue becomes critical when number of channels goes to several tens of thousand (eg 80000) or more (eg million-ish). Such image cubes become possible in future telescopes such as SKA or ngVLA or ALMA-WSU.