Fix incorrect BayesQuasi calculation

[robertapplin]

Description of work

This PR fixes a bug introduced in a recent PR (#37975), where the result workspace was not being constructed correctly after a BayesQuasi calculation using the quasielasticbayes package.

I have added a system test to so we have better test coverage for this algorithm.

There is no associated issue.

Report to: Spencer Howells

To test:

1. Open Inelastic Bayes Fitting
2. Go to Quasi tab
3. Load following sample and resolution

irs26176_graphite002_red.zip

irs26173_graphite002_res.zip

6. Click Run
7. Plot all in the Output options section of the GUI
8. You should get plots similiar to these two:
   

This does not require release notes because this is a regression

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[RichardWaiteSTFC]

Looks good, the results I get look good

Sorry about the stacking suggestion - I assumed the lists were flat!
At least it highlighted where you needed a test - thanks for adding it!