Merge pull request #460 in CASA/casa6 from CAS-12735 to master
* commit 'ece27617e4edc3bb09791f34c4215f9d6e34e399':
For CAS-12735, in Calibrater::genericGatherAndSolve, handle simdata_p=True case properly in Freq meta-data section so that c++ unit tests using SimpleSimVi2 will work properly (e.g., tCalibraterSolveSimData_GT); also added tests of FreqMetaData class to tVisCal_GT.cc
Removed leftover caltables from new frequency meta tests
For CAS-12735: Added tests for gaincal freq meta data improvements, using existing data in DR. (No change to existing tests)
For CAS-12735: In SolvableVisCal::discernAndSetSolutionFrequencies, fixed indexing of spwfanin for non-trivial combine='spw' case. Corrected some comments in ChannelAverageTVI::getChanWidths
For CAS-12735: More improvements in freq-meta calculation: (a) when append=T, check freq-meta consistency for spws already in the disk caltable, (b) add logging info about frqe-meta, (c) removed some couts left behind in previous commits
For CAS-12735: In SolvableVisCal.cc fixed bad cast syntax in previous commit that broke in casa6 build
For CAS-12735: introduce freq-meta calculation for solve globally before the solve starts, via new FreqMetaData class.
For CAS-12735 (cal freq-meta), added machinery to serve nominal channel width info (alongside channel frequencies) via ViImplementation2::getChanWidths function (cf getFrequencies). Requisite derivations also added to VisibilityIteratorImpl2, TransformingVi2, SimpleSimVi2, and (especially) ChannelAverageTVI. The getChanWidths function does not support arbitrary frame conversions on the widths (which would be very subtle, and which are not needed for the present context), and access is only available from the ViImplementation2 interface (no VisBuffer2 accessor, as yet). In ChannelAverageTVI, some adjustments made to make the bypass for the single-channel (degenerate) case in the getFrequencies and getChanWidths functions *not* depend on a call to visibilityShape() (which, in turn, depends on VI2 synchronization. This permits access to effective frequency and width info (including when averaging) for any spectral window outside the VI2 iteration loops in applications. (c++ unit tests for ChannelAverageTVI pending)
For CAS-12735, in Calibrater::genericGatherAndSolve, handle simdata_p=True case properly in Freq meta-data section so that c++ unit tests using SimpleSimVi2 will work properly (e.g., tCalibraterSolveSimData_GT); also added tests of FreqMetaData class to tVisCal_GT.cc
