Alter saving of QRF model

[gavinevans]

Related to https://github.com/metoppv/mo-blue-team/issues/877

Description
This PR alters the saving of the QRF model, so that the saving uses the clize functionality provided at the CLI level, rather than saving within the plugin.

Testing:

• Ran tests and they passed OK
• Added new tests for the new feature(s)

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (mobt_877_implement_qrf@9f7e1c8). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...oad_and_train_quantile_regression_random_forest.py	0.00%	2 Missing ⚠️
...r/calibration/quantile_regression_random_forest.py	0.00%	1 Missing ⚠️
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Additional details and impacted files

@@                    Coverage Diff                    @@
##             mobt_877_implement_qrf      #16   +/-   ##
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  Coverage                          ?   96.21%           
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  Files                             ?      142           
  Lines                             ?    14073           
  Branches                          ?        0           
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  Hits                              ?    13541           
  Misses                            ?      532           
  Partials                          ?        0           

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