Create task_config member variable upon initialization

[DavidNew-NOAA]

Description

This PR creates the task_config member variable in the Task __init__ function. Normally it is created upon initialization of a child subclasses of Task, but since it is expected to exist for every application of the Task class I've seen so far, it's better to create it at initialization.

This PR also eliminates runtime_config, since it's mostly redundant and renames the config member variable with a leading underscores to emphasize that they should be treated as private.

This PR is a companion to Global Workflow PR #2654 which replaces any reference to config or runtime_config member variables with task_config.

Type of change

• [X] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• [X] pynorms
• [X] pytests
• [X] GDASApp j-job tests
• [X] Cycling experiment on Orion with Global Workflow

Checklist

• [ ] My code follows the style guidelines of this project
• [X] I have performed a self-review of my own code
• [X] I have commented my code, particularly in hard-to-understand areas
• [ ] My changes need updates to the documentation. I have made corresponding changes to the documentation
• [X] My changes generate no new warnings
• [x] New and existing tests pass with my changes
• [ ] Any dependent changes have been merged and published

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 48.17%. Comparing base (8406bee) to head (c710e9f). Report is 8 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/wxflow/task.py	0.00%	6 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #30 +/- ## =========================================== + Coverage 47.93% 48.17% +0.23% =========================================== Files 18 18 Lines 1650 1642 -8 Branches 335 334 -1 =========================================== Hits 791 791 + Misses 799 791 -8 Partials 60 60 ```

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