LSPS2 Dynamic Channel Sizes

[aylagreystone]

In a similar vein to #559 and #560 an LSP might want to provide different users with different over provisioned channel sizes based on historic payment volume as a way to minimize on-chain costs and efficiently allocate capital. Initially we might want to be conservative with over provisioning as to not lock up liquidity in a channel that will not be used. However, on subsequent opens we would have a better sense of the volume we could expect from a user and adjust accordingly.

[tnull]

I think this is a subset of #564.