[Feature request] Allow separate minchansize setting for private channels

[openoms]

Currently a node operator can only control the minimum channel size accepted together in public and private channels:

lnd/sample-lnd.conf

Line 245 in fa4155c

; minchansize=

The setting is very useful:
Small public channels are not desirable for a routing node since they are uneconomical (large onchain cost vs usefulness) and getting unbalanced quickly causing payment failures.

There should be a separate setting to allow minimal sized private channels (alongside the different requirement for public ones) to allow mobile wallets and other small private nodes to choose freely.

This would allow for more decentralization without affecting path finding and the payment success rate.

[Roasbeef]

FWIW the enterprising node operator can implement something dynamic like this today using the existing channel acceptor APIs.