Mock subtensor with stakes

[kudroma1]

Bug

There are no stakes in metagraph.S that is created for MockSubtensor.
They are absent even if we add neurons using force_register_neuron() method.

subtensor_mock = MockSubtensor()
subtensor_mock.setup()
subtensor_mock.create_subnet(netuid)

for wallet in wallets:
    # It is important to use float number for stake and balance.
    # int is considered as rao. It is divided internally by 1e9.
    subtensor_mock.force_register_neuron(
        netuid=netuid,
        hotkey=wallet.hotkey.ss58_address,
        coldkey=wallet.coldkey.ss58_address,
        stake=bt.Balance(10000.0),
        balance=bt.Balance(10000.0),
    )

metagraph = bt.Metagraph(netuid=netuid, network=subtensor_mock.network, sync=False)
metagraph.sync(subtensor=subtensor_mock)
print(len(metagraph.S))

Description of the Change

Imlemeted methods query_runtime_api() to get subnet state and get_metagraph_info().

Verification Process

I ran tests locally to see that there are no regressions.

Branch Acknowledgement

[ ] I am acknowledging that I am opening this branch against staging

[basfroman]

fix all checkers and tests pls