Migrate Localisations To PHP vs JSON

[lrljoe]

This:

1. Reverts back to using PHP files for localisation
2. Splits tests so that Unit tests live in their own directory, and own test suite
3. Creates some basic Localisation tests in their own directory, and test suite.

This is to assist with:

1. Bugs associated with JSON localisation
2. Improving Localisation coverage

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

New Feature Submissions:

1. Does your submission pass tests and did you add any new tests needed for your feature?
2. Did you update all templates (if applicable)?
3. Did you add the relevant documentation (if applicable)?
4. Did you test locally to make sure your feature works as intended?

Changes to Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

[codecov]

Codecov Report

Attention: Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.

Project coverage is 87.73%. Comparing base (0c8ec45) to head (1649677).
Report is 154 commits behind head on development.

Files with missing lines	Patch %	Lines
src/Views/Traits/Columns/IsSortable.php	0.00%	2 Missing ⚠️

Additional details and impacted files

@@                Coverage Diff                @@
##             development    #2038      +/-   ##
=================================================
+ Coverage          87.30%   87.73%   +0.42%     
- Complexity          1672     1934     +262     
=================================================
  Files                150      184      +34     
  Lines               3891     4426     +535     
=================================================
+ Hits                3397     3883     +486     
- Misses               494      543      +49     

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