Add checkout settings for payment method behavior

Just jumping in here, patch 60 seems to be working in initial testing.

Merge request from 74seems to be missing the checkbox at checkout for some reason. @tBKot can you provide a patch and interdiff between #60?

I am seeing the same thing as @tonytheferg

patch in #60 seems to work, but the MR does not show the "Save this payment method for later use" checkbox on the checkout form.

Here is an interdiff of #60 and MR 149

It appears that with the MR, in order for the checkbox to appear on the checkout form, the payment gateway needs to have the public method

 public function supportsReusableOption(): bool {
    return TRUE;
  }

When it does, the checkbox appears and the payment method is stored at checkout when checked.

I think this is a good addition, but gateway contrib modules will need to support this.

Here's a patch version of the PR as of comment 74, along with patches for commerce_stripe and commerce_authnet to make them compatible.

I suspect those probably belong in the other modules' issue queues, but until we are sure this is how things are being done I think it makes sense to keep it all in one place.

I found that the patch above caused a crash on free orders that didn't have a payment method attached when trying to produce the payment information summary pane. The attached version makes a small check to avoid that crash.

Handling of free orders is actually not mentioned in the issue summary here but sneaked into the patch ;) Because currently we always make payment methods reusable, and here this option is squeezed under always reusable, I am creating ✨ Allow creating payment method on free orders Active and will extract the relevant part of #79 in there.

Currently not commenting on the reusability feature but will come back to comment on that soon.

Here are some objectives that should be included in this issue's scope:
- customer must be able to opt-out from reusable payment method (::setReusable(FALSE)). Non-reusable payment methods will only be used to create initial payment.
- gateway must be able to declare whether the payment method it creates is reusable. We must be able to filter out all unreusable payment methods. whether existing or new, depending on the context. For example, commerce_recurring must be able to enforce checkout with a reusable payment method for the sake of subsequent charges
- some gateways, depending on configuration, may be reusable but only in the Customer Initiated Transaction (CIT) scenario. This is already possible for Stripe. Such payment methods should not be reusable for Merchant Initiated Transactions (MIT). We must be able to filter them out ✨ Define payment method's reusability context Active

I don't think we currently have one but this probably calls for a meta issue so we can divide the scope into some smaller chunks and work on them one by one,