Fix mailer argument deserialisation for 6.1 on Ruby 3.1

[pirj]

I've cherry-picked #2566 to main.
Locally,on Ruby 3.1 it passed for 6.0 (to fix failing sub-builds) and for 7.0, too.

[pirj]

Without fixes from #2552, 7.0 builds expectedly fail.

What fails on 6.1 and 6.0 are those 2 scenarios.
It seems it needs more specs for various combinations depending on self.delivery_job = ActionMailer::MailDeliveryJob setting like even the same Rails version can have a different global or even a mailer-local setting for a job that affects serialization, e.g. mentioned here, and in our own specs:

    class UnifiedMailer < ActionMailer::Base
      self.delivery_job = ActionMailer::MailDeliveryJob
# vs
      self.delivery_job = ActionMailer::DeliveryJob

I can hack on it next week.

My impression is that we won't be able to make enuque_mail to match with both with({'foo' => 'bar'}, 1, 2) and with(params: {'foo' => 'bar'}, args: [1, 2]), so this will be a breaking change. I admit recklessly merging #2546 without noticing this change of behaviour.

[JonRowe]

@pirj I've merged this because I'm reconcilling the main branch with the released 5.1.1, my intent is to ressurrect the discussion around the changed behaviour in another branch on top of this