Decide and implement long-term solution for plot results checkbox in ISIS SANS GUI

[rbauststfc]

Under issue #37577 we implemented option A as a temporary solution to test the impact of removing the plot results checkbox on the ISIS SANS interface, while providing a quick mechanism for users to get this functionality back if needed. We agreed that it would remain in Mantid for three versions (in 6.11, 6.12 and 6.13) before deciding on and implementing the long-term solution. The long-term solution is expected to be one of the following:

• If no issues have been raised over the absence of the plot results feature, we should agree with the SANS scientists that we can remove the checkbox and supporting logic altogether. This will also involve removing the ability to set the feature via the user properties file.
• If we find over this period that the feature is needed then we will need to investigate and fix the underlying issue. We can then remove the ability to set the feature via the user properties file, as it will go back to being available all the time.

I will add this issue to the milestones for each future release so that we remember to review how things are going at each release period and can move to the longer-term solution earlier than planned if that seems appropriate at any stage.