This Commit fixes failing system tests in ISIS powder polaris.

re: #28415

this commit adds system tests covering the new rebin options in the polaris create total scattering script.

re: #28415

Accidentally removed inheritance of systemtesting.MantidSystemTest when
removing with_metaclass and add_metaclass. Put them back.

Removes all of the from __future__ imports that open and close the
brackets on the same line. This is most of them.

Also updated class_maker.py

Attempts to flush out the cause for the failing nightly clean build on
Windows. This is periodically failing on both the release / master clean
builds without any reason why.

Fixes all flake8 3.7.9 warnings as part of the Python 2->3 transition.

The stdDev function that was deleted in this branch often returns different values  than the 'correct' value which is sqrt(eigenvalue)  - which is now used. Typically the difference is  <0.5%, however occasionally the stdDev function returned a std deviation that is unrealistically small (by two orders of magnitude), this behavior is not as yet understood, but since the function is no longer used it is appropriate to change the test values.

This commit updates the reference files for tests where the transmission
workspace is output from ReflectometryReductionOne. The refactored code
in this PR has introduced a fix in this algorithm to output the
transmission workspace after it has been rebinned to detectors.
Previously it was output before the rebin step, hence the minor
differences in the output. Note however that the final results of the
reduction (IvsQ workspaces) are unchanged.

This commit also moves the code to set the output workspace to the
bottom of the function that does the transmission correction, to help
avoid a similar problem happening again.

Re #27633

When assigning to a list of outputs when calling the algorithm in
python, the outputs must be specified in the order they are declared,
even if they are optional outputs like IvsLam. This means that if we
want to specify the transmission workspace output we must first specify
IvsLam even if debug is false. Some of the algorithms always output
IvsLam if the name was given whereas others did not. They now always
output it if the name is given.

Note that this means you may now get an error if you don't supply enough
arguments whereas previously it was ok. It is ok if you just specify the
IvsQ output(s) but beyond that we do not know whether the output should
be IvsLam or the transmission, so we require all of them, hence the
error. This is better than it assigning an unexpected output so I think
is ok, and is the only way I can think to do this.

Re #27633

System tests for Abins are modified to calculate up to second-order
excitations only (as third and fourth-order are currently disabled.)

In addition, the test data for two other tests needs updating;
BezeneBinWidthCASTEP and TolueneScale have small changes in the
results. This is associated with a more conservative criterion for
discarding small values compared to the previous system; results
similar to the previous setup can be obtained by modifying the
threshold used in
SPowderSemiEmpiricalCalculator._calculate_s_over_threshold

Removes Python 3 only code (to comments where possible) since the next
release must be Python 2/3 Compatible

This commit adds system tests for the new fourier filter in powder polaris.

re: 27773

Adapt the command interface and user file parser to use sans state
objects, instead of the new containers (which duplicated the data
objects).

This is a large PR as we must change all call sites, partially unlink
the reading of run data (the dict converter still takes data info which
needs fixing), and create classes that facade the building process

As the state folder was starting to fill I also took this chance to move
them into their own package, so we have a seperation of data and impl

This commit adds system tests for the new fourier filter in powder polaris.

re: 27773

A new boolean parameter SimulateTracksForEachWavelength has been added to
the MonteCarloAbsorption algorithm. This exposes a switch on the MCAbsorptionStrategy
that was present before this change but was hardcoded to False.

The parameter NumberOfWavelengthPoints is only required if SimulateTracksForEachWavelength
is set to True. This change means that an attenuation factor is calculated for all wavelength
bins if SimulateTracksForEachWavelength=false. To facilitate this a performance enhancement
has been made to the Material class to calculate the total scatter cross section and the
absorption cross section once when the Material rather than every time these cross sections
are retrieved by the MonteCarloAbsorption calculation.

This change required some unit and system tests to be updated eg ILLDirectGeometryReductionTest
has been changed to remove the NumberOfWavelengthPoints parameter and the reference file to be
updated. To make this test more robust I have increased the number of scenarios used in the MC
simulation from 5000 to 20000

Also required updates to system test files. Updates to complexShapeAbsorptionsTest
include changes to increase number of scenarios and increase of tolerance so tests
are more robust to changes in random number sequences in MC simulation

A PeaksWorkspace is now iterable and no longer responds to
the table lookup api.
Refs #26839