Combine Local and Remote files into single tree

[AndrewTwydell]

What It Does
Resolves #416
Renames Local Files tree to Files, and adds Remote files to this same tree. Different context menu options are available, and different icons, but they share a parent Files tree. Same behaviour under a CICSplex, showing All Files rather than All Local Files

How to Test
Expand Files tree under a region with both Local and Remote files installed, and see both appear.

Review Checklist
I certify that I have:

• tested my changes
• added/updated automated tests
• updated the changelog
• considered whether the docs need updating
• followed the contribution guidelines

Additional Comments

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.31%. Comparing base (b4366fe) to head (069084d).

Additional details and impacted files

@@                 Coverage Diff                  @@
##           resource-fetcher     #459      +/-   ##
====================================================
+ Coverage             69.15%   69.31%   +0.16%     
====================================================
  Files                   164      165       +1     
  Lines                  3932     3953      +21     
  Branches                546      563      +17     
====================================================
+ Hits                   2719     2740      +21     
  Misses                 1213     1213              

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