Bug fixes for IG Repository

[JPercival]

• Update the Repository interface with some defaults for additional methods
• Fixed context value being auto appended to path
• Fixed support for external resources
• Fixed support for mixed XML/JSON igs
• Added support for conversion-on-write for IGs
• Removed string-based overload on IGRepo in favor of Path

[github-actions]

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[codecov]

Codecov Report

Attention: Patch coverage is 86.25592% with 29 lines in your changes are missing coverage. Please review.

Project coverage is 53.91%. Comparing base (073a8c6) to head (ed2d945).

❗ Current head ed2d945 differs from pull request most recent head dae3ba6. Consider uploading reports for the commit dae3ba6 to get more accurate results

Files	Patch %	Lines
...s/cqf/fhir/utility/repository/ig/IgRepository.java	81.69%	21 Missing and 7 partials ⚠️
.../cqf/fhir/utility/repository/ig/IgConventions.java	90.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #435      +/-   ##
============================================
+ Coverage     53.32%   53.91%   +0.58%     
- Complexity     2134     2162      +28     
============================================
  Files           281      280       -1     
  Lines         11843    11916      +73     
  Branches       1619     1632      +13     
============================================
+ Hits           6315     6424     +109     
+ Misses         4912     4863      -49     
- Partials        616      629      +13     

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