cln: Sanity check max htlc amount msat

[YusukeShimizu]

For #246 (comment)
Added logic to check the maximum htlc limit for cln set per node for each channel.
Additionally checking maxhtlc would be more strict than CLN's own limitations.

Also, to ensure that the receivable amout is also taken into account.

[grubles]

Tested ACK 6ab037a.

Using setchannel htlcmax=1 on the CLN node.

CLN as swap receiver:

$ ./out/pscli swapin --sat_amt 18420558 --channel_id 179134633420587008 --asset lbtc
2023/10/02 15:00:24 rpc error: code = Unknown desc = exceeding receivable amount_msat: 1

CLN as swap sender:

$ lightning-cli --signet peerswap-swap-out 162922x1x0 18670459 lbtc  
{
   "code": -1,
   "message": "exceeding spendable amount_msat: 1"
}

[nepet]

Ack 6ab037a