Document fees in bittensor

[MichaelTrestman]

there's a change to the fee structure, but this should be documented in general

New fee structures:

Most extrinsics now have a flat fee (~τ0.0013)
There is an additional 0.05% for staking, unstaking
This new flat fee is now paid out of free balance.
The 0.05% is paid in alpha for unstaking, and Tao for staking.

This flat fee should be reduced by 10X in an upcoming release (~τ0.00013)

There has been an ongoing insufficient liquidity issue on some testnet subnets (btcli error 7 and 14) that has been preventing these sns from being able to be staked to/unstaked from. The core issue has been identified, and should be fixed shortly.

Below is a list of the extrinsics which now have a flat fee which previously did not:
add_stake
add_stake_limit
remove_stake
remove_stake_limit
remove_stake_full_limit
move_stake
transfer_stake
swap_stake
swap_stake_limit
unstake_all
unstake_all_alpha
associate_evm_key

[MichaelTrestman]

include order of operations, and edge cases around being blocked by low balance/fee gotchas