isis_powder generate_run_numbers() support plus signs in filename list

[samtygier-stfc]

For POLARIS total scattering it is sometimes useful to sum non consecutive runs, e.g. 146554+146603 or 146554+146603-146609. This PR ensures that the POLARIS scripts can handle the plus operator to match Load behaviour.

Description of work

In the ISIS powder POLARIS script, the focus method need to get a flat list of all the file included in a filename string. It does not need the full filename parsing that exists in Load, so it has its own simple implementation. For this comma and plus operators are equivalent.

Converts '+' to ',' so that the existing parsing in IntArrayProperty will work correctly.

Adds tests

Closes #40648

To test:

Test script at:
#40648 (comment)
If it succeeds it will generate a workspace called test

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[RichardWaiteSTFC]

Maybe I'm doing something wrong - but I get the following error for the run number string "139966,139970-139973"

AttributeError: 'tuple' object has no attribute 'strip'

  File "C:\mantid-conda\mantid\scripts\Diffraction\isis_powder\routines\common.py", line 295, in get_first_run_number
    run_numbers = generate_run_numbers(run_number_string=run_number_string)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\mantid-conda\mantid\scripts\Diffraction\isis_powder\routines\common.py", line 208, in generate_run_numbers
    run_number_string = run_number_string.strip()

But when I call the function directly it seems to work...

generate_run_numbers("139966,139970-139973")
Out[2]: [139966, 139970, 139971, 139972, 139973]

Also I think there could be a unit test in this file

mantid/scripts/Diffraction/isis_powder/test/ISISPowderCommonTest.py

Line 4 in ecb712c

# NScD Oak Ridge National Laboratory, European Spallation Source,

[samtygier-stfc]

Maybe I'm doing something wrong - but I get the following error for the run number string "139966,139970-139973"

Are you sure you don't have something like:
sample_run_numbers = 139966,139970-139973
that would give you a tuple instead of a string, so strip() would fail.

Also, with a comma, it will still fail in generate_ts_pdf() because that can't handle a WorkspaceGroup. I could add a message for this (now I remember we discussed that.)

[RichardWaiteSTFC]

Thanks for adding test and handling error with group workspace. The error I saw was indeed a typo in my test script - thanks for spotting that! Happy to approve!