Use truly free balance (liquid) in chain extension

[gianfra-t]

Closes #483

Uses the reducible_balance fn from the Inspect trait. This is the truly liquid balance see here of orml_tokens and here for pallet_balances. Here frozen has a different meaning but the meaning of liquid is the same judging by how both use it in their transfer_all function.

There is no need to substract from reserved since these free and reserved are already mutually exclusive (see the reserve extrinsic).

Why not use MultiCurrency

Sadly, this trait does not implement the notion of a reducible balance nor of a frozen balance. It does implement this notion in ensure_can_withdraw but this won't actually tell us the amount, so the Inspect trait seems to be the only choice (that I could find).
But this means we need to match between the native and token variants, which is not very ergonomic. Also, the return is encoded to avoid mismatches of Balance type.

[ebma]

@gianfra-t is this ready for review? You didn't add reviewers.

[gianfra-t]

Yes @ebma it is, but tests are failing (I was waiting for them). I will check if it is related.

[gianfra-t]

I will ran format afterwards since it will as always complicate the review of actual changes.

[ebma]

Interesting, I didn't know about the reducible_balance function. Makes sense to use it but unfortunate that it's not implemented on the MultiCurrency trait.

Looks good to me overall 👍

[gianfra-t]

I merged this even if the CI showed a failure, because locally when running the last clippy commands they all work. It may have been a one time thing.

[TorstenStueber]

Is the failing CI due to clippy? Isn't it the Test job that fails with the following error?

Oct 14 13:51:18.446 ERROR parachain_staking::pallet: 💥 keeping old session because of empty collator set!

[gianfra-t]

But that has been a very common log we see almost always we start the chain in tests. I doubt it will make the CI fail.

It almost seems like it didn't run the last 3 jobs.

[gianfra-t]

Ohhh I checked the logs of the CI again and I see:

System.IO.IOException: No space left on device : '/home/runner/runners/2.320.0/_diag/Worker_20241014-124125-utc.log

So that's it.