active_storage: refactor concerns

Follow-up of #5953.

Refactor the concerns with two goals:

- Getting closer from the way ActiveStorage adds its own hooks.
  Usually ActiveStorage does this using an `Attachment#after_create`
  hook, which then delegates to the blob to enqueue the job.
- Enqueuing each job only once. By hooking on `Attachment#after_create`,
  we guarantee each job will be added only once.

We then let the jobs themselves check if they are relevant or not, and
retry or discard themselves if necessary.

We also need to update the tests a bit, because Rails'
`perform_enqueued_jobs(&block)` test helper doesn't honor the `retry_on`
clause of jobs. Instead it forwards the exception to the caller – which
makes the test fail.

Instead we use the inline version of `perform_enqueued_jobs()`, without
a block, which properly ignores errors catched by retry_on.

config/initializers/active_storage.rb

@@ -4,9 +4,14 @@ Rails.application.config.active_storage.analyzers.delete ActiveStorage::Analyzer
 Rails.application.config.active_storage.analyzers.delete ActiveStorage::Analyzer::VideoAnalyzer
 
 ActiveSupport.on_load(:active_storage_blob) do
-  include BlobSignedIdConcern
-  include BlobVirusScannerConcern
   include BlobTitreIdentiteWatermarkConcern
+  include BlobVirusScannerConcern
+  include BlobSignedIdConcern
+end
+
+ActiveSupport.on_load(:active_storage_attachment) do
+  include AttachmentTitreIdentiteWatermarkConcern
+  include AttachmentVirusScannerConcern
 end
 
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