In Stake2.0, query the amount of delegatable resources share of the specified resource type for an address; the unit is ram. Returns max_size - int64: the amount of delegatable resource share; the unit is ram.
When querying the delegatable energy share of an account, if the available energy share in the account is 0, this API returns {}.
When querying the delegatable bandwidth share of an account, if the bandwidth obtained by staking in the account is insufficient to cover the bandwidth consumed by a resource delegation transaction, this API also returns {}. Note: If the delegating transaction includes a memo, it will consume additional bandwidth, meaning the actual delegatable share will be lower than what is returned by this API.