Feature #2583 ecnt

[JohnHalleyGotway]

This PR adds 2 new output columns to the ECNT line type.

• IGN_CONV_OERR and IGN_CORR_OERR
  These are only computed when observation error information - specifically the assumed error distribution - is provided via the config file or in the MET_OBS_ERROR_TABLE.

Expected Differences

• Do these changes introduce new tools, command line arguments, or configuration file options? [No]
  
  If yes, please describe:
  

• Do these changes modify the structure of existing or add new output data types (e.g. statistic line types or NetCDF variables)? [Yes]
  
  If yes, please describe:
  
  Adds 2 new columns to the existing ECNT line type.

Pull Request Testing

• Describe testing already performed for these changes:
  
  Ran unit_ensemble_stat.xml and confirmed that the OBS_ERROR output files are updated as expected. Manually ran Stat-Analysis jobs (-job aggregate -line_type ECNT and -job aggregate_stat -line_type ORANK -out_line_type ECNT) to confirm that they produce consistent output.

• Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
  
  Please review:

  • Documentation updates:
    • Ensemble-Stat Ensemble Observation Error
    • Ensemble-Stat ECNT Line Type Table
    • Appendix C Observation Error Logarithmic Scoring Rules
  • Differences in the ECNT output of the regression test flagged by this GHA testing workflow run.
  • The code for this PR for additional testing is compiled by the met_test user in seneca:/d1/projects/MET/MET_pull_requests/met-12.0.0/beta4/MET-feature_2583_ecnt/bin.

• Do these changes include sufficient documentation updates, ensuring that no errors or warnings exist in the build of the documentation? [Yes]

• Do these changes include sufficient testing updates? [Yes]
  Updates the output of the existing OBS_ERROR unit test in unit_ensemble_stat.xml.

• Will this PR result in changes to the test suite? [Yes]
  
  If yes, describe the new output and/or changes to the existing output:
  
  Modifies existing output.

• Please complete this pull request review by [Mon 3/4/24].
  

Pull Request Checklist

See the METplus Workflow for details.

• Review the source issue metadata (required labels, projects, and milestone).
• Complete the PR definition above.
• Ensure the PR title matches the feature or bugfix branch name.
• Define the PR metadata, as permissions allow.
  Select: Reviewer(s) and Development issue
  Select: Milestone as the version that will include these changes
  Select: Coordinated METplus-X.Y Support project for bugfix releases or MET-X.Y.Z Development project for official releases
• After submitting the PR, select the ⚙️ icon in the Development section of the right hand sidebar. Search for the issue that this PR will close and select it, if it is not already selected.
• After the PR is approved, merge your changes. If permissions do not allow this, request that the reviewer do the merge.
• Close the linked issue and delete your feature or bugfix branch from GitHub.