Add algorithm for creating POLREF transmission workspaces

[rbauststfc]

Description of work

Summary of work

A new algorithm that implements the pre-processing steps described on the linked issue. See the "Calibration runs" section for a description of what is required. The purpose of the algorithm is to pre-process the magnetic and non-magnetic calibration runs taken on POLREF so that they are ready to pass to the PolarizationEfficienciesWildes algorithm.

Fixes #35682.

Further detail of work

This PR includes a few workarounds in order to prevent delays to the work. However, ideally more fundamental fixes should be found, so I will open issues for the following:

• It seems that you cannot retrieve the output workspace group from an OutputWorkspace property when an algorithm is run as a child on a workspace group. As explained in the comment in the code, I have implemented a workaround, but it would be good to try and resolve this at source at some point (Calling child algorithms with workspace groups doesn't populate output workspace property #38473).

• The Divide algorithm sets the YUnit to an empty string and the distribution flag to True if two workspaces with the same units are divided by each other. However the Mantid Integration algorithm performs the integration differently for distribution data as it assumes that it means the counts in the workspace have been divided by the bin width. The apparent discrepancy between the two definitions of "distribution" can lead to incorrect results when we create the transmission workspace after a flood correction (due to the use of the Integration algorithm within CreateTransmissionWorkspaceAuto in order to normalize by monitors). In this PR, I have manually set the flood corrected workspace back to a non-distribution as a workaround.

To test:

This implements a workflow that the POLREF scientists have already implemented in their own code, so I have validated against their results to check that the new algorithm produces equivalent results.

The reviewer should run the new algorithm and check that the validation is robust. The following script can be used to do that:

out_grp = ReflectometryISISCreateTransmission(InputRuns=["POLREF32130", "POLREF32132"], ProcessingInstructions="272-290")

The algorithm docs should be built and checked to ensure that they are easy to understand, and there are no spelling and grammar issues.

I have run a build from branch to check that the system test passes on all operating systems, although this was a few weeks ago now so could be repeated by the reviewer if they want to.

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[adriazalvarez]

Thanks for adding this algorithm. I have followed the test instructions and the transmission workspace is created with the intended properties. Additionally, unit tests and system tests are passing. The docs are well formatted and clear to follow.
I have few -minor- suggestions and questions, but otherwise it looks good.

[adriazalvarez]

Thanks for taking the time to address my comments.
I approved as the changes won't affect the test output.