Ensure nomination pool members can directly stake and vice versa.

[Ank4n]

Context

As a side effect of #3905, it becomes possible for a direct staker to reuse the staked (frozen) funds to be used for participating in a pool (hold) as well. Essentially double staking with the same funds.

This is prevented currently by pallet-delegated-staking not allowing direct stakers to delegate, as well as by pallet-staking only taking free balance into account.

Task

As a followup to #5501, remove the condition to not be a direct staker for bonding to pool.

[rainbow-promise]

Hello @Ank4n I would like to take this issue.

[Ank4n]

Hello @Ank4n I would like to take this issue.

@rainbow-promise Thanks for your interest. This issue can only be done post #5501, and only requires one line to remove. I would suggest to pick up an issue with C1-Mentor.