Fix: Explicitly include src/ directory when compiling PHAR

[localheinz]

This pull request

• removes the autoload configuration before running tests with PHAR
• explicitly includes the src/ directory when compiling PHAR because humbug/box apparently filters out directories named Test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.88%. Comparing base (0019770) to head (c561045).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #598   +/-   ##
=========================================
  Coverage     61.88%   61.88%           
  Complexity      116      116           
=========================================
  Files            28       28           
  Lines           585      585           
=========================================
  Hits            362      362           
  Misses          223      223           

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