[DEFECT] MultivariateNormal distribution class errors out when being loaded from a pickle file

Thank you for the defect report

[X] I am using the latest version of RAVEN.
[X] I have read the Wiki.
[X] I have created a minimum, reproducible example that demonstrates the defect.

Defect Description

The ravenframework.Distributions.MultivariateNormal class pickles successfully and appears to unpickle successfully. However, some attributes of its parent class NDimensionalDistributions like workingDir are not saved on pickling, so calling the getInitParams method of MultivariateNormal causes the unpickled distribution to error our with an AttributeError.

This bug affects the ravenframework.TSA.VARMA class.

Steps to Reproduce

The following short script reproduces the error. I ran this from the raven base directory.

import os
import pickle
import numpy as np
from ravenframework.Distributions import MultivariateNormal

# Initialize a MultivariateNormal distribution object
dist = MultivariateNormal()
dist.method = 'pca'
dist.dimension = 2
dist.rank = 2
dist.mu = np.zeros(2)
dist.covariance = np.eye(2).ravel()
dist.workingDir = os.getcwd()  # must be set or errors on pickling
dist.initializeDistribution()

# Pickle and unpickle the object
pk = pickle.dumps(dist)
dist2 = pickle.loads(pk)

# fails with "AttributeError: 'MultivariateNormal' object has no attribute 'workingDir'"
dist2.getInitParams()

Expected Behavior

All attributes set and stored by the parent class should also be recovered when pickling the child class. This should enable all class methods to execute properly after unpickling.

Screenshots and Input Files

See "Steps to Reproduce" for a minimum working example. The output of that example on my machine is shown in the included screenshot.

OS

MacOS

OS Version

14.3

Dependency Manager

CONDA

For Change Control Board: Issue Review

[x] Is it tagged with a type: defect or task?
[x] Is it tagged with a priority: critical, normal or minor?
[x] If it will impact requirements or requirements tests, is it tagged with requirements?
[x] If it is a defect, can it cause wrong results for users? If so an email needs to be sent to the users.
[x] Is a rationale provided? (Such as explaining why the improvement is needed or why current code is wrong.)

For Change Control Board: Issue Closure

[x] If the issue is a defect, is the defect fixed?
[x] If the issue is a defect, is the defect tested for in the regression test system? (If not explain why not.)
[x] If the issue can impact users, has an email to the users group been written (the email should specify if the defect impacts stable or master)?
[x] If the issue is a defect, does it impact the latest release branch? If yes, is there any issue tagged with release (create if needed)?
[x] If the issue is being closed without a pull request, has an explanation of why it is being closed been provided?

idaholab / raven