Replace puts in tasks and generators with Rails.logger or Logger.new

[mamhoff]

Summary

We should not use puts here, but instead the configured Rails logger. A log level of info is appropriate for all of these instances.

In the Dummy App generator, Rails is not yet loaded, so we use the normal logger instead.

Extracted from #6240

Checklist

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[codecov]

Codecov Report

Attention: Patch coverage is 30.76923% with 9 lines in your changes missing coverage. Please review.

Project coverage is 88.82%. Comparing base (6426bb3) to head (0a0313a).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
core/lib/spree/testing_support/common_rake.rb	0.00%	4 Missing ⚠️
core/lib/spree/testing_support/translations.rb	0.00%	2 Missing ⚠️
core/lib/generators/spree/dummy/dummy_generator.rb	0.00%	1 Missing ⚠️
...rs/solidus_promotions/install/install_generator.rb	0.00%	1 Missing ⚠️
...tions/lib/solidus_promotions/promotion_migrator.rb	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6244      +/-   ##
==========================================
- Coverage   88.82%   88.82%   -0.01%     
==========================================
  Files         850      850              
  Lines       18334    18336       +2     
==========================================
+ Hits        16286    16287       +1     
- Misses       2048     2049       +1     

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[tvdeyen]

@mamhoff there is a valid spec error https://github.com/solidusio/solidus/actions/runs/15340861947/job/43166600606?pr=6244