Add signal to sigma post fitting check

[MohamedAlmaki]

Description of work

This pull request introduces a new property to FitPeaks and PDCalibration: the option to set a minimum signal-to-sigma ratio for post-fitting. When this property is provided, peaks with a signal-to-sigma ratio below the specified minimum will be rejected. The signal-to-sigma ratio is calculated as the integrated fitted peak minus the integrated background, divided by the sigma, which is calculated using the quadrature sum of the errors.

Fixes #35224.

To test:

1- Run the following script:

from mantid.simpleapi import *

ws = CreateSampleWorkspace(Function="User Defined",
                           UserDefinedFunction="name=LinearBackground, A0=0.3;name=Gaussian, PeakCentre=5, Height=10, Sigma=0.7",
                           NumBanks=1, BankPixelWidth=1, XMin=0, XMax=10, BinWidth=0.1)

FitPeaks(InputWorkspace='ws', PeakCenters='5.1', FitWindowBoundaryList='0,10', OutputPeakParametersWorkspace='fitted_params',
         BackgroundType='Linear', FittedPeaksWorkspace='fitted', OutputWorkspace='peakpositions', MinimumSignalToSigmaRatio='200')

2- Check the fitted data and params, you will notice the peak has been rejected.
3- Rerun the same script but with MinimumSignalToSigmaRatio='150', then you will see the expected fitted peak.

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[RichardWaiteSTFC]

Thanks for this, the calculation of I/sigma looks good.
Just some suggested changes and would it be possible to add a test and release notes for this .
Sorry I haven't been able to test this yet due to boost update requiring a new build, but I will do manual testing once comments addressed. Thanks!

[RichardWaiteSTFC]

Code looks good - but I think there may be something wrong with the I/sigma calculation.
It looks to me like the I/sigma of the peak in your test code should ~12

intens = np.sum(ws.readY(0) - ws.readY(0)[0])
sigma = np.sqrt(np.sum(ws.readE(0)**2))
print(intens/sigma)  # 12.24

It looks to me though that FitPeaks only rejects the peak around ~100
Can you see what's going on?

[sf1919]

@MohamedAlmaki This looks like genuine test failures.

[MohamedAlmaki]

Yes, I am working on fixing it

[RichardWaiteSTFC]

Thanks for this - looks good. Now in test script the chi-squared of the peak gets set to DBL_MAX around I/sigma ~ 12