Improve file filtering for submission execution

Previously, many different executions got all files despite not necessary needed. We now extend the file filtering to apply for submit actions, remote evaluations and test executions, too.

app/models/submission.rb

@@ -218,10 +218,16 @@ def prepared_runner
       files = collect_files
 
       case cause
-        when 'run'
-          files.reject!(&:reference_implementation?)
-          files.reject!(&:teacher_defined_assessment?)
-        when 'assess'
+        when 'run', 'test'
+          files.reject! do |file|
+            next true if file.reference_implementation?
+            # Only remove teacher-defined assessments if they are hidden.
+            # Otherwise, 'test' might fail if a teacher-defined assessment is executed.
+            next true if file.teacher_defined_assessment? && file.hidden?
+
+            next false
+          end
+        when 'assess', 'submit', 'remoteAssess', 'remoteSubmit'
           regular_filepaths = files.reject(&:reference_implementation?).map(&:filepath)
           files.reject! {|file| file.reference_implementation? && regular_filepaths.include?(file.filepath) }
       end