Updates following review

[gavinevans]

Addresses metoppv#2135

Description
This PR addresses review comments made in metoppv#2135. This PR also corrects handling within the CLI if the forecast and truth parquet files are both present but don't contain the required times. In this situation, the QRF model can not be trained.

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 11 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (mobt_877_implement_qrf@5d74839). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...oad_and_train_quantile_regression_random_forest.py	0.00%	8 Missing ⚠️
...r/calibration/quantile_regression_random_forest.py	0.00%	3 Missing ⚠️
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Additional details and impacted files

@@                    Coverage Diff                    @@
##             mobt_877_implement_qrf      #21   +/-   ##
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  Coverage                          ?   95.60%           
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  Files                             ?      142           
  Lines                             ?    14177           
  Branches                          ?        0           
=========================================================
  Hits                              ?    13554           
  Misses                            ?      623           
  Partials                          ?        0           

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