Silence Minitest for plugin tests.

Fixes #17340.

Use Minitest::BacktraceFilter instead of removing all silencers. This
will allow the backtrace for all libraries in the plugin to be shown
while removing noise generated by Minitest's backtrace.

railties/lib/rails/generators/rails/plugin/templates/test/test_helper.rb

@@ -10,7 +10,9 @@
 <% end -%>
 require "rails/test_help"
 
-Rails.backtrace_cleaner.remove_silencers!
+# Filter out Minitest backtrace while allowing backtrace from other libraries
+# to be shown.
+Minitest.backtrace_filter = Minitest::BacktraceFilter.new
 
 # Load support files
 Dir["#{File.dirname(__FILE__)}/support/**/*.rb"].each { |f| require f }

railties/test/generators/plugin_generator_test.rb

@@ -57,6 +57,7 @@ def test_generating_without_options
     assert_file "test/test_helper.rb" do |content|
       assert_match(/require.+test\/dummy\/config\/environment/, content)
       assert_match(/ActiveRecord::Migrator\.migrations_paths.+test\/dummy\/db\/migrate/, content)
+      assert_match(/Minitest\.backtrace_filter = Minitest::BacktraceFilter\.new/, content)
     end
     assert_file "test/bukkits_test.rb", /assert_kind_of Module, Bukkits/
   end