Add some methods and initialize task_config in task class

[DavidNew-NOAA]

Description

This PR causes the the "task_config" member AttrDict object to be created in the init method of the "Task" class. Previously, "task_config" has been created separately, but all applications that utilize the "Task" class expect "task_config" to exist, so it might as well be created at initialization. Example of task_config creation: https://github.com/NOAA-EMC/global-workflow/blob/67b833e0c7bc390865d453588b4609a1a7ede981/ush/python/pygfs/task/atm_analysis.py#L59

This PR also adds two class methods to the "Task" class:

1. j2yaml_to_filehandler: Parses a Jinja2-templated YAML and then passes the resulting dictionary to the file wxflow FileHandler. This is a common task when staging files for various jobs that can be consolidated into a class method. Example: https://github.com/NOAA-EMC/global-workflow/blob/67b833e0c7bc390865d453588b4609a1a7ede981/ush/python/pygfs/task/atm_analysis.py#L78
2. extend_task_config: Takes a dictionary or AttrDict object and merges it with the "task_config". This is a common task done when initializing Task objects. Example: https://github.com/NOAA-EMC/global-workflow/blob/67b833e0c7bc390865d453588b4609a1a7ede981/ush/python/pygfs/task/atm_analysis.py#L59

This PR is part of a broader refactoring of pygfs in the Global Workflow.

Type of change

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

How Has This Been Tested?

• [x] pynorms
• [x] pytests

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 25.00000% with 12 lines in your changes missing coverage. Please review.

Project coverage is 47.91%. Comparing base (8406bee) to head (7b5f330). Report is 8 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/wxflow/task.py	25.00%	12 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #29 +/- ## =========================================== - Coverage 47.93% 47.91% -0.03% =========================================== Files 18 18 Lines 1650 1657 +7 Branches 335 336 +1 =========================================== + Hits 791 794 +3 - Misses 799 803 +4 Partials 60 60 ```

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