Re #19286

Re #19286

Re #19286

Re #19286

Re #19286

Re #19286

Re #19286

Re #19286

This maintains the previous behaviour: we assume that if the input is in
wavelength then the reduction has already been done.

- Fix an inconsistency when summing in Q where normalisation by
transmission run was not being done if the input workspace is already in
wavelength, whereas this normalisation is always done when summing in
lambda. Both methods now always normalise by transmission run.
- Fix an inconsistency when summing in Q where cropping of the output
workspace was not being done.

Re #19189

MonteCarloAbsorption expects the sample to be centered at the origin.

Re #19189

- Add unit tests for summing in Q with normalisation by:
  - direct beam
  - monitor
  - transmission run
  - correction algorithm
- Add a unit test to check IvsQ when summing in Q.

- Previously the unit tests were using 3 detectors at the same position.
This commit changes them to be at different positions, which is required
for meaningful tests for the summation in Q functionality.
- Some test results have therefore changed as a result of the new
detector positions. To limit the changes, I have used processing
instructions of "2" where only a single detector is used. This is the
centre detector and has the same position as it did previously.
- The order of the processing instructions in the tests for multiple detector groups have
been modified to check that the resulting groups are being sorted correctly.
- Unit tests for summing in Q added.

When summing in Q, make the output order the same as when summing in
lambda. The latter uses GroupDetectors, which orders the groups by the
first spectrum number in the group. This commit sorts the detector
groups in the same order so it will be the same for any further
processing.

This adds a unit test for a case where spectrum numbers are different in
the transmission and run workspaces, but mapping between them is not
done because StrictSpectrumChecking is set to false.

This tests an attempt to normalise by a transmission run with strict
spectrum checking enabled but where the requested spectrum does not
exist in the transmission run