Move permission sets back to app/

[mamhoff]

These were already in app, but moved in #403, attempting to fix #344 (A copy of Spree::PermissionSets::DefaultCustomer has been removed from the module tree but is still active!)

At the time of that PR, code reloading was still handled by Rails, so let's see if we can now move them back as Zeitwerk now handles code reloading.

[codecov]

Codecov Report

Attention: Patch coverage is 64.00000% with 135 lines in your changes missing coverage. Please review.

Project coverage is 88.69%. Comparing base (b1b8567) to head (fba1c16).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...els/spree/permission_sets/configuration_display.rb	0.00%	30 Missing ⚠️
.../models/spree/permission_sets/dashboard_display.rb	0.00%	19 Missing ⚠️
core/lib/spree/permission_sets.rb	0.00%	5 Missing ⚠️
core/lib/spree/permission_sets/base.rb	0.00%	5 Missing ⚠️
...lib/spree/permission_sets/configuration_display.rb	0.00%	5 Missing ⚠️
.../spree/permission_sets/configuration_management.rb	0.00%	5 Missing ⚠️
...ore/lib/spree/permission_sets/dashboard_display.rb	0.00%	5 Missing ⚠️
core/lib/spree/permission_sets/default_customer.rb	0.00%	5 Missing ⚠️
core/lib/spree/permission_sets/order_display.rb	0.00%	5 Missing ⚠️
core/lib/spree/permission_sets/order_management.rb	0.00%	5 Missing ⚠️
... and 10 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6090      +/-   ##
==========================================
- Coverage   89.28%   88.69%   -0.59%     
==========================================
  Files         813      829      +16     
  Lines       17906    17989      +83     
==========================================
- Hits        15987    15956      -31     
- Misses       1919     2033     +114     

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[tvdeyen]

Makes sense. Thanks for the house keeping as well.