fix: panic in asset callbacks against native account

[PhilippGackstatter]

Fixes asset callback against the native account panicking due to attempting to start a foreign context against the native account.

This is fixed by checking if the active account is already the target of the callback invocation, and if so, skips starting (and ending) a foreign context against it.

The PR implements the check against the active account rather than the native account, which seems equivalent but also a bit more future-proof. For instance, if we allow mutating a transaction during FPI in the future, then during an FPI call against faucet A, the faucet itself might add an asset that it has issued to a note, which would trigger a callback against itself. In this case, the faucet is the active account, but not the native account.

For now, during callback checks, if faucet_id == active_account_id, then active_account_id == native_account_id, due to the native account assertions in the output_note_add_asset and account_add_asset kernel procedures.

PR targets main since this seems to be the branch from which we still release.

closes #2864

[PhilippGackstatter]

Will merge this to unblock @onurinanc and for easy cherry-picking into next.

If possible, would be good to get a review from @bobbinth post-merge anyway.