Metagraph async

[ibraheem-opentensor]

Async migration for the following modules:

• metagraph.py
• commands/metagraph.py
• metagraph in subtensor

[thewhaleking]

@ibraheem-opentensor hey I didn't get a chance to review this, but let's update this:

difficulty = await subtensor.difficulty(cli.config.netuid)
subnet_emission = bittensor.Balance.from_tao(
    await subtensor.get_emission_value_by_subnet(cli.config.netuid)
)
total_issuance = bittensor.Balance.from_rao(
    (await subtensor.total_issuance()).rao
)

to

difficulty, subnet_emission_, total_issuance_ = await asyncio.gather(
    subtensor.difficulty(cli.config.netuid),
    subtensor.get_emission_value_by_subnet(cli.config.netuid),
    subtensor.total_issuance()
)
subnet_emission = bittensor.Balance.from_tao(subnet_emission_)
total_issuance = bittensor.Balance.from_rao(total_issuance_).rao

We want to take full advantage of asyncio with big push.