Fix updateNeuron not to change the neuron subaccount

[dskloetd]

Motivation

Currently when you use updateNeuron on the GovernanceTestCanister for testing, there is no way not to change the neuron subaccount in the process while probably you would never want to change the neuron subaccount.
This is because when calling update_neuron the full neuron, including account (which is the neuron subaccount) must be specified but nns-js never returns the neuron subaccount. It only returns the accountIdentifier which is derived from the subaccount in a one-way fashion.

The current implementation of using the accountIdentifier as the neuron account is wrong and results in the neuron account changing each time updateNeuron is used.

So in order not to change the subaccount when calling update_neuron (and without changing the API of nns-js) we must first fetch the neuron to know its subaccount.

Changes

1. Change toRawNeuron (which is only used in updateNeuron) to take an account parameter to use for the raw neuron.
2. Change updateNeuron to first fetch the existing neuron in order to use its account to pass to toRawNeuron.
3. Verify that the account of the fetched neuron matches the accountIdentifier of the passed neuron to make sure people don't try to change the accountIdentifier while it's not supported.

Tests

1. Unit tests added
2. Tested manually by adding maturity in NNS dapp and seeing that the neuron account doesn't change.

Todos

• Add entry to changelog (if necessary).

[github-actions]

size-limit report 📦

Path	Size
@dfinity/ckbtc	7.91 KB (0%)
@dfinity/cketh	3.49 KB (0%)
@dfinity/cmc	1.29 KB (0%)
@dfinity/ledger-icrc	3.88 KB (0%)
@dfinity/ledger-icp	15.22 KB (0%)
@dfinity/nns	34.76 KB (+0.41% 🔺)
@dfinity/nns-proto	140.98 KB (0%)
@dfinity/sns	15.71 KB (0%)
@dfinity/utils	4.47 KB (0%)
@dfinity/ic-management	2.78 KB (0%)

[mstrasinskis]

Thanks!