Protect channel account dusting: introduce channel state bloat bond

Background

So channel state bloat is indirectly deterred by the fact that there is a storage bag state bloat bond which is put up, and all channels have 1-1 relationship with lifetime of a dynamic bag. However, there is still the problem of the channel account risking getting dusted, as outlined here https://github.com/Joystream/joystream/issues/3497, for this reason we may as well introduce a state bloat bond, as it is functionally a solution to the state bloat bond. Moreover, dynamic bag bloat bonds are going away: https://github.com/Joystream/joystream/issues/3580

Dependency

https://github.com/Joystream/joystream/issues/3580

Proposal

Add state bloat bond, paid by creator at point of channel creation, and returned to whomever deletes channel. Fund with membership of caller, even if curator group or lead.

An alternative solution which could have served the same purpose would be to just mint this upon channel creation, however, as we are removing bloat bonds for dynamic bags (https://github.com/Joystream/joystream/issues/3580), a genuine user funded bloat bond is now needed to solve both state protection and channel account dusting.

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